Warning: SPOILERS ahead for the Agents of S.H.I.E.L.D. season 5 premiere
Agents of S.H.I.E.L.D. is designed to flesh out the world of the MCU while occasionally basing its narrative on the Marvel movies themselves - and we're fast approaching the release of the biggest and most impactful MCU movie yet - Avengers: Infinity War. Most of the films merely get a nod or an homage, but both Captain America: The Winter Soldier and Avengers: Age of Ultron have factored prominently into the show's storytelling. The Winter Soldier kicked off a new status quo for the series that radically reworked it during the final section of its first season. Agents of S.H.I.E.L.D.'s second season, meanwhile, laid the groundwork for the Helicarrier that served as the deus ex machina in Age of Ultron.
When season 4 of Agents of S.H.I.E.L.D. ended by bringing the team into space, it seemed impossible that the show and Avengers: Infinity War wouldn't somehow connect. After all, how could the now spaced-based agents not pitch in when Thanos came calling. But the season 5 premiere of Agents of S.H.I.E.L.D. threw a spanner into the works by establishing that events were not only set in the future, but that the Earth had been destroyed. It's all but guaranteed that Marvel's flagship TV series will react to Avengers 3 when it arrives toward the end of season 5 in May, but Agents of S.H.I.E.L.D. already be tying into Infinity War?
Did Thanos Blow Up The Earth?
With the one-two punch of the Avengers: Infinity War teaser trailer finally dropping and Agents of S.H.I.E.L.D. revealing season 5 is set in a future where the Earth has been destroyed, it didn't take long for fans to start wondering if the Mad Titan was responsible. There's no doubt that Thanos coming to Earth and gathering the Infinity Stones will have a monumental impact on the MCU, and Avengers 4 will likely deal with the fallout of the film. But even if Agents of S.H.I.E.L.D. doesn't get renewed for another season, it will still have a number of episodes set to follow the debut of Avengers: Infinity War.
The series has always found new and innovative ways to tell its own story while still playing into the events of the larger MCU, and there's no doubt that the culmination of the entire shared universe to date will deeply affect the show. What's more, the episodes following Infinity War's release could be the very last we see of Agents of S.H.I.E.L.D. With that in mind, it's not a stretch to imagine that, like in season 1, the show is already telling its post-Infinity War story.
The second half of Agents of S.H.I.E.L.D. season 5's two-part premiere teased the idea that Quake was responsible for the Earth being torn apart. Given how TV shows work, this may just be a red herring - especially since even in the comics Daisy has never had power on that level. The idea that Thanos' war on Earth destroys the planet isn't at all far-fetched, though it does seem like a rather bombastic way to end the movie. Still, it could be a reason for the Avengers and their allies to head to space for Avengers 4, taking the fight to Thanos and more closely mirroring The Infinity Gauntlet comic.
The big issue with this theory, however, is that while the writers of Agents of S.H.I.E.L.D. certainly know the story and fallout of Infinity War at this point, it's hard to imagine season 5 of the show is built around a spoiler for the end of Avengers: Infinity War. A more likely scenario is that Agents of S.H.I.E.L.D. is in one version of the future.
The Darkest Timeline
When Agents of S.H.I.E.L.D. revealed it wasn't set in the present, many began assuming this would free the show from having to tie into the films. This idea only works if the show is set in the past, though, as being in the future means they have even more of the MCU to address. It's clear the agents are at least 100 years past the point of the Earth being destroyed, making the writing a continuity minefield if it's supposed to address everything that will happen in the films. But with the Time and Reality Stone in play for Avengers: Infinity War, it seems more likely the agents are merely in one version of the future.
The concept of an alternate reality doesn't guarantee that Thanos is the reason the Earth no longer exists in Agents of S.H.I.E.L.D., but it would allow the show to follow that thread without spoiling next year's film. This would complicate things a bit, as the show would either have to hold back on that reveal until around May or risk discussing the potential events of a film that's yet to arrive. But if this is Agents of S.H.I.E.L.D.'s last season, we could see it go out with a narrative bang.
Even if Thanos isn't responsible, it seems safe to assume the show is either in an alternate timeline or will somehow travel back home later in the season to prevent what's unfolding. And given how most season's of the show have been at least thematically, if not narratively, tied to Marvel's biggest film of the year, there's a good chance the destruction of the Earth and Agents of S.H.I.E.L.D.'s future setting will have something to do with Avengers: Infinity War.