I'm not sure I agree. That there was a trap was obvious, I think, but this doesn't mean there was necessarily an alternative way for Putin to react without losing face. I imagine the forces that move this kind of things along have a form of inertia measured in years or decades. Especially if there are other forces (backers, allies, whatever) goading him and pushing his government to take action. Maybe he thought the alternatives were worse.

I think it's evident now Putin made a mistake, even by his own calculations, and that it might be too late for him to back off now.