in my tenure I’ve only seen a couple reasons why people have lost their blogs
- hoarding urls (don’t know the limitations on this but probably 15+)
- posting misleading/malicious things
most recently it appears these blogs were washed because they were reblogging a scam post about diet pills (scammers paid them money to reblog a scam) which I’m sure is against the TOS.
I bet they can get their blogs back though; tumblr most likely did it as a strict warning to get them to stop, so everyone celebrating that they’re gone is being a bit preemptive