One day, they do it once too many, and a lot of people switch. This makes it more easy for the remainers, so some more of them switch. So you don't get a gradual decline, you get an avalanche.

The big entity finally takes notice, rolls backb the last chance, but people keep leaving. They don't realize they have to rollback all unpopular decisions, not only the last one, plus give people a reason to choose them over all others.

So the powerfull entity bleeds dry. Either it keeps a hard core of remainers that take any abuse thinkable, allowing them a hollowed out existence for a long time. Or some other powerfull entity gobbles up the remnants. In extreme cased, the big entity just desintegrates, unable to minimally sustain itself.

You see this pattern with big corporations, with governements. The catholic church in Europe seems another example. In fact, I fear what we're doing to the planet might become the mother of all examples.