Sometimes the call looks wrong from where you are standing. The job change, the money, the way they are handling their own family.
What you can be confident in isn't the outcome but the process: that they think things through, that they would tell you if it went badly, that they have been right before about things you doubted at the time.
Trusting somebody's judgement means letting them make a decision you would have made differently, and then not spending six months quietly collecting evidence. Say your piece once, properly, and be on their side afterwards.