Unfortunately it's a fairly common pattern among humans, people don't prepare ahead of time for disasters that have "never happened before." Or that haven't happened in their lifetime. Especially when those preparations cost them something, be it time or money or effort.

It's been long enough since Digg that this generation didn't believe that it would happen to Reddit too. Maybe someday it might happen to the Fediverse, somehow - there's only so much you can do with protocol design alone to proof against centralization, we're already seeing some interesting cracks around the Beehaw defederation mess.