Exactly like all software developers who thought they were going to make games or some world changing application at least in their own time, and then five years later they are just logging out for the day and playing games or streaming crap all evening like everyone else.
Given how many great open source projects there are, some developers actually do that. Just not me and you bro.
A lot of FOSS is maintained by people who are getting paid one way or another to maintain it.