Distraction
It is rather horrendus to start a war to distract from other things that are bothering you, or just because you want to. or even because you have to.
Your poll numbers are going down,
The Epstein files are making things worse.
You like to pretend that you are a big tough guy - even though you never did military service.
People who did favours for you are calling in their cards.
So you start a war - unfortunately you are not the first president to do that - against the rules of your own country and that of the United Nations. You spend lives and tax payers money to do that. You learn nothing from the experience of previous wars started for questionable or illegal reasions. You don’t learn. The question is whether anyone else will.
We don’t know.