There are lots of sites where moderators don’t make a point to look for underage users, but by policy have to cut them off when they come across them. I’ve seen scenarios before wear a spurious flag for some thing irrelevant ends up having this outcome.
https://docs.github.com/en/site-policy/github-terms/github-t...
Presumably because of https://en.m.wikipedia.org/wiki/Children's_Online_Privacy_Pr...
Sorry to hear you've lost access to your accounts. That really sucks.