OK. Time Travel in this movie.
Probably I am going to fuck this up but at the current time this is my best understanding.
The timeline we have been watching all along for all these movies is Timeline 1 (TL1).
In TL1 Thanos gets the stones and does the snap. Then 5 years later the Avengers invent/discover time travel. OK.
The events of Endgame are TL1s present.
Can they just go back and kill baby Thanos? No.
Why not? Because that won't change their future. It will create a kind of branching timeline. So, a potential Timeline X that has no Thanos but that will not be TL1 so it doesn't work. That's some other timeline NOT our TL1. Good, I got it.
So the Avengers go backwards in TL1 and remove the Infinity Stones from various points in TL1.
As the Ancient One explains to Bruce Banner, this will create branching timelines (TL2, TL3, TL4, TL5 and TL6) for the removal of the time and mind stones from NY, the space stone from the 1970s, the power stone from Morag, the soul stone from Vormir and the reality stone from Asgard.
So now the present TL1 has all of the stones but there are 5 new timelines out there going along without their stones. Got it.
Then Thanos also removes himself from one point in TL1 and inserts himself at a different point in TL1. Thus creating another timeline TL7 that now does not have a Thanos.
In TL1 Thanos lived, snapped and died AND ALSO jumped forward in time and died again thus creating but not closing off TL7.
Thor kills TL1 Thanos and Tony also kills a younger version of TL1 Thanos. This second death leaves TL7 without a Thanos (I will come back to this).
After the big battle Captain America goes back in time and returns Mjolnir and the six stones to the exact points where they were taken and thus closes TL2, TL3, TL4, TL5 and TL6. That's fine. Those 5 loose ends are tied up since now those timelines never came to be. OK. Or at least those 5 alternate realities have their stones back.
In theory this should mean that Black Widow never dies because Cap replaces the stone just before Hawkeye gets it. However this leaves her stuck in the past of TL1. Cap also decides to deliberately leave himself stuck in the past of TL1 after he returns the stone in the 70s.
Does this mean that they have created a branching TL8 and TL9 since Cap and Widow were removed from their TL1 present thus creating 2 alternate timelines where they didn't just live on and die of old age in like 2070 or something? Instead they lived on in TL1s past instead of TL1s future. Thus creating two new branches, TL8 and TL9. Hm?
Sooo... there is a timeline/reality out there, TL7, without a Thanos that broke off when Thanos left TL1 at an earlier point and never returned to close that loop. That means TL7 has no Thanos, no collecting the stones, no snap.
Right?
Does this mean that when Dr Strange looked at 14,000,605 possibilities in Infinity War he was looking at approx 14 million alternate timelines?
And the only one where the snap doesn't happen is the one that has no Thanos?
At the conclusion of Endgame the TL1 Avengers didn't really win. The undid the snap and they killed Thanos for a second time BUT Thanos already did the snap and the sheer number of casualties and consequences of removing 3.5 billion people for 5 years and then popping them back into existence will have bad consequences.
HOWEVER by doing all this they did manage to goad Thanos into a confrontation that ultimately left a single timeline without a Thanos.
Since that Thanos never did return to his rightful place in time, and since we know what we know from Banner and the Ancient One, there has to have been a timeline now going along where Thanos has been removed. So this is the one in 14 million chance that Dr Strange saw.
Ultimately the Avengers victory was two-fold. They undid the snap for their own timeline BUT the real victory was that they managed to goad a version of Thanos away from TL1 and kill him, thus creating the ONLY timeline/reality where they never even had a snap.
I think I got it.
