That's a good point as well; you need projects like BDK, LDK, #[5] ... when there is enough tooling and project is recognizable enough, easier to get budget for regular events and bring devs.
https://twitter.com/fulmolightning did a lot of hacker days that popularized Lightning... and looked exactly as your pic. Not sure why those stopped, probably funding problems.
Maybe we need to start monthly #Nostr Hack Days!