Or maybe the questions were innocent and legitimate, but another listener realised the value of the answers?

The article says "During Q&A, the future attacker asked a few very legit, on topic questions".

Sure, but it doesn’t state how they knew that the speaker was the attacker… perhaps this was one of the details that they couldn’t tell us about, but absent that, it is fair to question why they are so sure. Especially if the video is public and the questioner could be identified.

This raises further questions - if they aren’t worried about unmasking their attacker, why not go ahead and name & shame them in the article, instead of giving away just enough information to enable a witch-hunt?

They already had the person's name by that point. They traced the attack back to the attacker, and had already figured out they weren't an employee or associate of an employee.

As the article points out, a great many people - usually completely innocent - ask questions exactly like this.

I don't know if you assume that malicious actors wear hoodies and sunglasses and use voice-changers all the time or what, but in my experience, the best covert operations happen in plain sight.