I look at it as "the beginning of the end." It's crossing the event horizon in a black hole.
The GOP has successfully created an alternate fictional reality for the majority of voters, but once free press has been suppressed, there can't be competing realities. There's almost certainly no going back because the state propaganda at that point is the only game in town, and no oppositional narrative can take hold.
I wish people would have left earlier as well, but it's not just sunk cost fallacy. Network effects are a rational reason to stay, and that's the issue. If he has a community, he loses the community. I get it.
That's why I wish celebrities would coordinate and all leave at once - it's far more likely their network will follow them in that case, both hurting X more and helping themselves more, and accelerating people leaving as the network effects disappear on X.
The physics metaphor applies pretty directly here: They need to create momentum to counteract inertia.