Obviously a few years ago, the API changes caused the reddit community mods to strike, and caused a mass-blackout of most reddit core communities. Eventually Reddit removed a handful of mod teams on some notable subreddits and caused the rest to chicken-out. But it did birth the Fediverse properly.
I suspect Reddit will make another step at some point which causes another comparable exodus. This time, if they do, the Fediverse is far better developed to handle it. What do you imagine it might be?
The single community I’m still visiting (read-only) on old.reddit has recently dried up to tumbleweed territory. I could stop going there overnight, and not miss a thing.