This question is based on my assumptions/understandings of the following:
- Way back in the past there was a multiversal war
- "He who remains" fought his variants and won the war.
- "He who remains" united all timelines into one main one before the event of any films we watched.
- What we watched as the MCU movies happened while "He who remains" was taking care that no branching happens.
- At some point "He who remains" dies, and branching started to happen.
We know that up to the point of Loki stealing the Tesseract and being taken by the TVA, there was no branching in the main timeline. Some time after that "He who remains" dies and branching started.
Also in Loki we learned that the TVA allowed the Avengers to time travel as it was meant to be (Avengers: Endgame)
So we should be sure that no branching happened at least to the point of Thanos defeat in Endgame.
Do we know or is it possible to know at what point of what we watched as the MCU movies the branching started?