Spammers have been programmatically creating accounts on Mastodon instances for years. Sometimes they post once and never again, sometimes they post on a schedule. Sometimes they never post, like a waiting botnet.
As Mastodon's anti-spam solutions are effectively nonexistent, most instances in our network require manual approval of new accounts. Up until recently, it was easy to spot a spammer; their join reasons were generic.
ChatGPT spammers have now arrived.