Banning an ip block is always a bonehead move. Its trivial for an attacker to change ips, fix the root problem.
The sort of people who could do that back then generally had much better things to do with their time. And resources. When you’re dealing with idiots who only have access to dialup or their university computer lab, it doesn’t take much to stop them. It was just a bunch of 20 year olds trying to have fun. Not defense networks.