How do Souls work in the MCU multiverse?
Doctor Strange foresaw all these possible futures with only one successful one.
However Endgame expanded this to the concept of "many worlds" and distinct universes being formed based on each decision made / action taken. So in some of these universes the heroes will take the wrong decisions and die. However we can assume they'd all be true to their characters and trying their absolute best.
When it comes to what we see at the end of the movie though, that is only the one outcome which worked out for the best as far as Doctor Strange saw it. However clearly this was not the best possible future for Thanos! Therefore would Thanos' soul travel down a different path, to a different universe, where he'd still be alive?
And vice versa can we assume that our heroes' souls continued down the path we see at the end of Endgame as they survive longer on this path?