TBH I'd just have found it contrived and boring. I wouldn't be excited to have colleagues who couldn't just talk about normal stuff at lunch.

One reason for the lunch is to try and relax a bit and test “cultural fit”, which is more like a blind date between two people to see if there is any spark. Ideally it is a two way conversation, where the candidate and the interviewers get to judge each other.

There is a problem where cultural fit “tests” are heavily biased against minorities - for example most any sports discussion is dominated by your social class.

Enjoying brain teasers matches a particular type of geek, and the discussion likely veered or was encouraged in that direction by the candidate. It wasn’t Machiavellian, which perhaps you are more responsive to?