Superman & Lois might actually be setting up the Crime Syndicate of America through Captain Luthor as opposed to Injustice. Since the beginning of Superman & Lois, Wolé Parks' Captain Lex Luthor has been one of the biggest mysteries. While he, like most versions of the iconic Superman foe, hates the Man of Steel, this new iteration is quite different. Not only is Luthor from an alternate reality, but he also has a new background compared to Jon Cryer's Lex Luthor.
While it's unclear what Earth he came from, Superman & Lois' Luthor is from a universe where an evil Superman destroyed his world. A flashback has shown Tyler Hoechlin in the black Superman suit again where he executed several soldiers, including that Earth's General Sam Lane. That's why Luthor is trying to convince Earth-Prime's Sam that the Man of Steel isn't a hero and that they need to take precautions before it's too late. With the setup of Project 7734, it seemed like the Arrowverse was possibly hinting that this Luthor comes from an Earth that is inspired by the Injustice franchise.
However, Superman & Lois might actually be adapting a different iconic DC storyline where Clark is also evil in an alternative reality. Injustice is just one of the handful of different Earths in the DC Multiverse where Superman is an antagonist. Rather than base Luthor's Earth on the popular Injustice video games, Superman & Lois might actually be introducing the Crime Syndicate of America into the Arrowverse.
Earth-3 & Crime Syndicate Explained
While Arrowverse fans may know Earth-3 as the original home of Jay Garrick, it has a different meaning in the comic books. The Crime Syndicate of America is an alternative version of the Justice League that lives on Earth-3 in the DC Multiverse. The pre-Crisis on Infinite Earths version of Earth-3 is the reverse of the main DC continuity, where the heroes are evil and the villains are the good guys. In that reality, the Justice League is known as the Crime Syndicate, with Ultraman (Superman), Superwoman (Wonder Woman), Johnny Quick (The Flash), Owlman (Batman), and Power Ring (Green Lantern).
Together, they ended up taking over the world. But as the Crime Syndicate discovered the Multiverse, they became obsessed with wanting to fight their counterparts. However, the existence of the Crime Syndicate also came the good versions of various DC villains, including Alexander Luthor Sr., who would instead refer himself as Alex while his son Alexander Luthor Jr. became that world's Lex. Earth-3 is eventually destroyed during Crisis on Infinite Earths and everyone but Lex survives.
The Post-Crisis take on Earth-3 is slightly different from the original iteration, especially the way The New 52/DC Rebirth eras have presented it. The Crime Syndicate has more members, including Superwoman now being an evil Lois Lane instead of a corrupted Wonder Woman. But based on the fact that Superman & Lois showed what Luthor's version of Lois was like in his world, it seems they're drawing more from the pre-Crisis Earth-3 dynamic. It all stems from the fact Luthor was married to Lois in that reality, which was also the case on Earth-3 in the older comics.
Alexander Luthor & Lois Lane's History
In the original version of Earth-3, Alex was married to Lois and together they had a son, Lex Jr. On Earth-3, Lois was still a talented reporter but worked for the Daily Star instead of the Daily Planet. Lois was also one of the characters who learned of superheroes existing on other Earths. When Crisis on Infinite Earths happened, Earth-3 was wiped out of existence. However, while Alex and Lois died when the anti-matter destroyed their world, they managed to send Lex Jr away, making him the only survivor of Earth-3.
In Superman & Lois season 1, episode 5, "The Best of Smallville", Luthor introduces himself to Earth-Prime's Lois, posing as a freelance reporter offering to help her with Morgan Edge. But it's made very clear that Luthor has feelings for Lois, as he keeps telling his A.I. that she's just like Lois of his world. The only thing that differed was who Lois was married to, as it's revealed that Luthor and she were married in their universe. So Luthor lost his father-in-law when Superman murdered Sam Lane. That's why Superman & Lois' Luthor is trying to get to the Lane family as early as he can so that he doesn't lose them again.
Luthor is fully convinced that every version of Superman in the Multiverse is destined to become evil, just like the Superman he faced in his universe. That's what led Luthor to give Sam on Earth-Prime the idea for Project 7734, so that this world can be prepared if/when Clark goes dark. Since he faced Superman in his world, Luthor is also more knowledgeable about the Man of Steel, which is why he's a few steps ahead.
How Superman & Lois Has Setup Earth-3 Thus Far
Originally in the Arrowverse, Earth-3 was Jay's homeworld, but when The CW adapted Crisis on Infinite Earths, that universe was erased like all the others. However, Oliver Queen as the Spectre rebooted the Multiverse and has brought back multiple Earths. But things are obviously different since Earth-2 is now the official designation for Stargirl, and John Wesley Shipp's character is going to be retroactively changed to have always been the Golden Age Flash of that world. So in a Post-Crisis Arrowverse, Earth-3 seems to have possibly become its comic book counterpart where Superman is now evil, fitting Superman & Lois perfectly.
What Superman & Lois have established so far is that, in Luthor's world, he was a soldier who served in the military. At some point, Luthor and Lois were married, with their first flashback having her tell him to come back before they parted ways. When the series first revealed that Luthor came from an alternate universe in which Clark was evil, it was in the middle of a mission. While the context is still missing, a black-suited Superman used his heat vision to kill several of Luthor's allies as well as Sam. How Luthor managed to get to Earth-Prime is also a mystery, as he even told Clark in the pilot that, somehow, he survived.
There's the possibility Oliver Queen had Luthor sent to Earth-Prime when the Multiverse was restored. However, Superman & Lois' Luthor still has memories of his world being destroyed by Superman. It's possible the events Luthor has gone through are taking place post-Crisis where Earth-3 still somehow was destroyed again because of the evil Superman. It's also worth noting that Luthor's description of his world being destroyed isn't necessarily literal speaking. Luthor could have meant that, because of the corrupted Man of Steel, his reality was no longer possible to live in.
Why Crime Syndicate Could Fit The Arrowverse
Following Crisis on Infinite Earths, the Arrowverse heroes on Earth-Prime have no idea that the Multiverse is actually back again. As far as they're concerned, Earth-Prime is the only world that survived the Crisis. At some point, whether it's this season or a few years from now, the heroes of Earth-Prime have to discover there are alternative worlds again. It will especially become crucial for when they can do crossovers again, since the global pandemic is currently making that tricky.
Superman & Lois may be the perfect gateway to not only bring that concept back into their lives but also introduce the Crime Syndicate. Obviously, the Arrowverse's Crime Syndicate would look a little different since they don't have Green Lantern, Batman, or Wonder Woman to make evil versions of. It's more likely that they would do evil versions of Batwoman, Black Lightning, and Supergirl, among others to join corrupt versions of Flash and Superman. It's also always fun whenever the actors get to do something different, especially when they portray villainous versions of their heroes. Whether it's Grant Gustin as Johnny Quick, Hoechlin as Ultraman, or Javicia Leslie as Owlwoman (likely what Earth-3's Batwoman would be called), there are a lot of possibilities.
If Crime Syndicate follows the same motives in the comics, it would make perfect sense for the Arrowverse incarnation to begin exploring other Earths. Through Superman & Lois, it could be the Crime Syndicate that makes Earth-Prime learn of the Multiverse again. It will always be tough to top Crisis on Infinite Earths, as that was the most ambitious Arrowverse crossover, but there are still worthy DC stories that are big and perfect to adapt for live-action. Through Luthor on Superman & Lois, the Crime Syndicate of America could finally get their due in live-action in the Arrowverse, which might be a better fit for The CW than Injustice.