Ok, but unless the future is deterministic, meaning there's no effective branching past Strange's choice, then there's million other futures where Tony doesn't do that thing.
How can Strange know he will do that thing? Either saving Tony sets them on a path where events are set in stone and the mouse will always do that thing (or rather, there's only one universe and timeline unless someone makes a change, meaning the statement about futures where the rat doesn't touch the button mean the Russos don't really know what they're saying) or there must be some influence Strange had to ensure that out of million possible outcomes, the rat would do its thing in that specific timeline.
The Russos stated that among the million futures Strange saw, only in a few the rat did what he needed to do. They also state he saves Tony because Tony is needed for the snap. So what does he do to ensure the rat does his part?
