10 Twisted Timelines Created By Avengers: Endgame
3. 2012: The Ancient One Knows Too Much
Even after that, when she returns to New York in 2012 after returning the remaining Infinity Stones, the Ancient One will be a time traveller herself, one armed with the certain foreknowledge of what happens in the future (as opposed to the myriad future possibilities that the Time Stone allows her to scry)... as well as the current locations of every one of the Infinity Stones.
The thing is, the Ancient One has a history of bending the rules to suit herself, justifying it by claiming she’s protecting the universe. She’s been prolonging her own life with dark magic for centuries, and Banner’s tale confirms something she’d only suspected up until now - that her long, long existence will end in 2016, when she passes the baton on to Stephen Strange.
The Ancient One doesn’t know Strange at this point except through her studies of future possibilities - she tells Banner that Strange is “supposed to be the best of us”. In 2017’s main timeline, when she taught Strange, she had continued to break the rules she has set in place and actively encouraged him to do the same… whatever it takes.
Power corrupts, absolute power corrupts absolutely, and the Infinity Stones are the definition of absolute power. All it takes is one decision to use her foreknowledge - or worse, to recover another of the Stones, even all of them. After all, the universe is safer in her hands than the broken hands of an arrogant surgeon. Isn’t it?