They shouldn't have brought them back... (Spoilers)

The infinity stones I mean, they should not have given them back after they've used them. Not only was it useless, it probably guaranteed the doom of those different timezone instances.

Let me explain.

Originally there was just one single timeline. We'll call this the main timeline. When they went back and grabbed the stones from the past, each of those timezones split-off into their own individual alternate timeline/reality because something was changed in them. Therefore to make sure they didn't break off into alternate timelines, the Avengers figured they'd bring back the stones to the exact moment they took them so that nothing seems to have changed and they don't end up breaking off into alternate realities. Sounds good so far right?

Except that by bringing back the stones to their original timezones and by making sure they stayed in the main timeline, that basically guarantees that they all result in "the snap" happening. That's what happens in the main timeline: Thanos wipes out half the universe and then destroys the stones.

Now you might say "but the Avengers fixed that by snapping all those people back to existence again". Well, not quite, not in the main timeline anyway. (At least this is how I understood it)

By bringing infinity stones from different timezones back into the present and then using it to revive half the universe's population, the Avengers effectively split themselves off into a different timeline (because they introduced something that was foreign to their timeline). They made an alternate timeline. So that ending of Endgame where they get to bring everyone back? That's now in an alternate reality. It never happened in the main timeline - that one still ends with half the population gone.

So the Avengers never should have brought back the stones to their original timezones. Yes, it would have made numerous alternate timelines but at least those timelines would be able to avoid "the snap". Because if that timeline is missing an infinity stone or two, Thanos would never be able to complete the IG in those alternate realities.


P.S. - there are now 4 timelines currently active in the MCU:
1. The main timeline that still ends up with half the universe decimated.
2. The new alternate timeline where the Avengers win and bring back half the universe.
3. The alternate timeline where Loki escaped with the Tesseract.
4. The alternate timeline where Cap is still alive in the past and marries Peggy.

*This means that there should have been no way that old Cap could have had his farewell talk with Falcon since they exist in different realities. .