I only notice that the other servers (which are also kind of well-known out there) only receive a few attacks per day, while the Tor nodes receive well over a hundred each (would be significantly more w/o fail2ban).
So I was wondering whether a botnet is currently targeting Tor nodes in particular.
Security researchers use lists of known public Tor nodes for legitimate testing purposes all the time. I remember seeing a few people on Tor mailing lists scan the network for open CUPS ports when that vulnerability first came out. If legitimate folk are already scanning relays, it’d make sense that malicious threat-actors would follow suit. Reiterating what others have said before, the best way to avoid this sort of thing is to not expose SSH or non-relay services at all.