There were 3 issues at once, so "trust & safety" is definitely part of it.
Too much traffic use, this is purely a billing issue and CF probably wouldn't even care (they haven't for years) despite losing money
Violating ToS with the domains, a minor infraction probably, but enough to cancel the contract
This is the big one: CF uses one pool of IPs for all customers, the IP of a gambling site (like a casino) will get banned by ISPs of various countries (Gambling being illegal, strictly regulated and so on). This is the trust & safety issue, CF is actively hurting by keeping this customer. The enterprise plan they want to push them to has ByoIP (Bring your own IP), which would probably have been one condition of keeping them on. CF could have communicated better (if we got the full story here..), but for $250 a month they'd much rather kick the customer off their service