What magic would he do? Be specific. Why is it not impossible? What other option would he have thought of? Come on. You’re making the assertion, provide proof. Heck even Trump hasn’t said he could have stopped this. So maybe you should pay attention to him. He understands world history and trying to prevent wars enough to know when one world leader really really wants to get into a war (which clearly Putin did) you can’t do anything.
Like I got a crystal ball? Really, your funny.