Pretty simple why it's illegal. They made up fake people, contact info, and email addresses that weren't tied to real people. The terms of the site don't allow that and when you are buying tens of thousands of tickets, people tend to notice.
There must be more to this story.
I'm not sure what the exact rules are for requiring a real identity to be linked to a corporate credit card. In this case, the broker's corp cards were not being used in the same way a typical employee would expense a purchase to the business. Rather, Wiseguys was just making up fake identities, and providing their own employees real identities for cards(this was the mistake that got them noticed). All of this is pretty straight forward financial fraud on the banking side of things, and not Ticketmaster's ToS.