Ticketmaster offers two-factor authentication. Was this enabled when the tickets were stolen?
If so, their 2FA stinks, it isn't doing its job, and they need to implement a more secure method.
If not, everyone who has an account with them should enable it immediately.
That goes for any other important accounts, too. I'm not necessarily on board with the push to eliminate passwords entirely, but by themselves, they are not enough to protect anything of real value.