Kevin Feige reveals why all of the original Avengers survived Thanos' genocidal snap in Avengers: Infinity War. Marvel's epic crossover was very different from most MCU installments in that it saw its villain achieve his or her ultimate goal. After acquiring the six Infinity Stones, Thanos used the Gauntlet's power to wipe out half of the universe's population, leaving those left scrambling to make sense of it all. Of course, some heroes had to be left alive in order for there to be an Avengers 4, and savvy viewers picked up on something shortly after Infinity War's premiere.
The characters who did turn to dust, such as Spider-Man, Black Panther, and most of the Guardians of the Galaxy, are newer faces of the franchise who weren't around during the Phase 1 days. That old guard, led by Iron Man, Captain America, and Thor, are still around, and Feige admits that's not a coincidence. Things were planned to happen this way.
In an interview with io9, Feige touched on the Infinity War survivors, providing a glimpse into Marvel's thought process when crafting the two films (which were shot back-to-back):
“I think for a film series that is going on 10 years and is gearing towards a conclusion with Avengers 4, which you don’t usually have in these kind of movies, you can sort of do the math. And realize it’s the original Avengers that are left.”
It's long been said Infinity War and Avengers 4 act as the culmination of the MCU to date, essentially closing one book before starting a new one. With that in mind, it makes sense to give the original six one last hurrah before they bow out and pass the torch. Of course, Iron Man, Captain America, and friends will be getting extra help in the form of Rocket, Ant-Man, and Captain Marvel, but chances are much of the focus will be on the heroes who first laid the foundation for the MCU and helped make it what it is today. Contracts are expiring and with the franchise successfully integrating a bevy of new heroes the past few years, a case can be made that Marvel has grown beyond that first team Nick Fury put together. Audiences will always love what those specific characters represent, but they can only go on for so long.
Infinity War's bold ending drew criticism in some circles because most viewers know (despite how Marvel tries to spin things), Peter Parker, T'Challa, and other "deceased" heroes aren't actually gone. They'll all return to lead their sequels in Phase 4 (some of which start filming in the near future), but perhaps this was the best decision for Avengers 4. Infinity War's roster of characters was so bloated, arguably the only way to give the Phase 1 crew the proper sendoff they deserve was to clear the deck and eliminate most of the newcomers. Now, there's more time to concentrate on the veterans one last time.