>Yes, because they managed to monetize their traffic and keep it up despite fierce competition (attempts... by Google, for example).
They didn't have to do anything, that's the point. They have such strong network effects. They would have to completely fuck up to lose even a tiny fraction of their userbase.
But they do have to do something. In fact, they're constantly doing a whole bunch of somethings to keep people in their ecosystem.
Apps. Messenger. Instagram.
They didn't get that network by just being first(ish). They got it by continuously being the best of the imperfect options, and they can lose it just as easily.
They didn't have to do anything, that's the point. They have such strong network effects. They would have to completely fuck up to lose even a tiny fraction of their userbase.