nostr:npub1zegknjw0z3ahy327qn64h4jypm7amzyk640gnjsrq3zhfya9095qf9p4ug that's fair honestly. Didn't think about that but you're absolutely right.
nostr:npub1vktd0c5c783644n33ea69n82gz9jfdqq5yysd8umsnuppzj2du2qle7z8m I don't think it's too surprising - even in Japan, Mastodon is more well known than Misskey, and while the platforms can obviously talk to each other, they probably figured it'd be better to pick a platform more people are familiar with.
Further, Misskey is more about "expression" and "fun", Mastodon has more of a "professional" air about it.
Discussion
nostr:npub1vktd0c5c783644n33ea69n82gz9jfdqq5yysd8umsnuppzj2du2qle7z8m As a quick follow up actually: NERV has been on ActivityPub since April 2017, which is before Misskey implemented ActivityPub (this was in 2018 sometime). No point moving I suppose.
Their account is nostr:npub1ghmf7w0askd92uj2cck2x88kn8ezk6pa4zq86j6qqd8ykrrhkrdsg7vhth.