Everybody has their own personal lines in the sand. People need to work for a living because we're not in a magical, post-need society. Every company has its flaws. Each company has some subjective amount of flaws/sins/evil, and everybody makes their own decision about what they're willing to do for money.

Helping a company use some sleazy dark patterns to make some extra money off of Taylor Swift tickets is honestly pretty mild on the scale of evil software engineering jobs, so I imagine their answer is "I built a system to sell entertainment, now my kids get to go to private school, and I sleep great at night."

Ticketmaster sucks, but it's not like he's working for Palantir, Lockheed Martin, or TikTok.