In general I don't think law enforcement wants discord to take these down or ban them. These guys would have no problem to just make some IRC servers or whatever to hang out on instead, which would be much harder to surveil for law enforcement - compared to discord just forwarding them everything said by those accounts and on those servers.
I know several people whose Discord accounts were banned because they participated in a server that later had some talk of illegal activities in one of the channels. There are similar stories all over Reddit.
In the same scenario, even if Walmart is right about who they ejected 75% of the time then they still have ~1 shoplifter remaining and ~1 very upset person.
Even in an ideal world where Walmart is right about ejection 100% of the time it doesn't mean they start receiving 0 new shoplifters either, it just means the number of people wrongly made upset is 0.
Discord's problem (on both ends) lies in lack of depth in investigating bans. It takes resources to review when someone shouldn't be banned and it takes resources to make sure you ban everybody. Putting too low of resources into banning just means that both sides of the scale manage to get tipped in the wring direction at the same time.
It’s basically impossible. They have money, IPs, identities, anything you could possibly want to evade.
They aren’t requiring age verification for everyone to join servers and chat. The headlines and panic really got away from the actual story.
Also, how would you even go about classifying them as botnet operators?