At that point they had all been running their meetups for 5-10 years, so they were also established in their careers and didn't NEED them anymore. So while keeping an existing meetup running pre-COVID was not exactly easy, it was doable and familiar.
But now, 5 years after COVID, all the longstanding meetups are long enough gone that people nearly have to start from scratch. It's starting to happen, but is a huge uphill battle. For the most part, I suspect it will be a new generation of organizers, but they'll be learning all the same lessons again, in a much less interesting and more hostile tech environment.