Q: How did Mastodon become so popular in Japan?
A: An exceptionally good article in "ASCII" magazine by Satoshi Endo, a long-time computer researcher in Japan, based in part on setting up and running his own Mastodon instance (8-p.net). That's a journalistic standard I'd like to see more in the West.
http://ascii.jp/elem/000/001/465/1465842/