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Non Sequitur Causality, though frequently this can be justified by For Want Of A Nail- that is, something as simple as changing someone's schedule by a few seconds can have rippling effects that drastically change outcomes.
See also Analysis.Story Branching for more on the way interactive stories play with this concept.
This might also be Schrödinger's Gun.
Schrodinger's Gun already has a bunch of video game examples where the ending you get, or other in-game choices you make, retroactively change the backstory.
I didn't write any of that.
Do we have a trope where Multiple Endings contradict one another? Obviously that's true in general, what I'm getting at is let's say you get ending A by choosing option A. And then you get Ending B by choosing option B. You realize in order to get those two endings far more would have to be different in the world then just making a choice. The motivations and actions of characters as revealed by the endings would have to be completely different and yet it's only revealed by those endings which again you only get by making a dialogue choice. That's one example.