Most crawlers aren’t going to come from ASN which are populated with eyeballs.
Fail2ban, by default, bans an IP for a limited time. For me that's 20mins.
This means that commonly only about 30 IPs are on the banlist. The chance that anyone using the same IP as a bot who is visiting any of the apps and sites on that server is not 0%, but tiny.
The only goal is to stop bots and worms from hammering my server. It hardly improves security; it shouldn't anyway.
nobody own their IP, and at some point a legitimate person will be assigned that IP
and most people who do bad things on the internet use some proxies, usually residential ones
it always makes me sad when people put such rules