Ask HN: How to determine grumpiness in job candidate?

New experienced hire (30+ years old) passed the interviews, with a few odd remarks about some software/companies that didn't trigger red flags for us. The criticism seemed misplaced but understandable.

After the welcome phase, where we showed him all the challenges we had and how much work was left, this became his common behavior:

- Excessive sighing when exposed to technical debt

- Switching between patronizing attitude and aloofness

- Sarcastic comments about internal processes (or lack of); as a matter of fact, about everything that gets discussed.

This is a team where members have total freedom to identify opportunities for improvement and carry them on. We have a flat structure (there's a manager on paper but the team is expected to work things out).

We were expecting, due to his experience and our clear indication that there was a lot to do and many projects would be greenfield, that he would be more excited about the work.

The thing is, he has always worked for small companies or startups, where one is supposedly used to lack of hierarchy and getting things done. So this attitude caught us by surprise.

I feel the extra grumpiness and the flood of technical challenges broke him. Some have theorized we were too extreme when presenting the situation and should have let him discover things by himself instead. The fact is, all of that can be fixed and we were hoping to speed the process up, because we knew what needed fixing (but didn't have enough time, thus the hiring).

How to better spot this during the interviews? Is grumpiness the issue here?