I’m with you in respect of the fact Trump only does what is good for him.
But I think there are a few more things going on here. He has spoken about bagging the Nobel Peace prize which feeds into the legacy stuff you are talking about. In addition, Trump is new money. A continuation of the war is worth nothing to him. Those American billionaires and millionaires making the dollar out of sales to the US government of arms sent to Ukraine are not his people, they are old money.
He wants to get the contracts for oil, gas and rare earths in Ukraine. He wants the property and rebuilding deals in Ukraine, he wants the sort of business ties and money making opportunities he thought the Bidens had there.
Trump sees money and opportunity for himself in peace. That’s why I think he’ll get it.
Trump may think that if Russia has Ukraine's land, he can do a deal with Russia to get some of the resources there. The resources belong to Ukraine, so maybe Trump thinks he can do a deal with Putin to share them, so they both win. But I don't see Ukraine and Europe going for it, so the war continues.
If Trump can't get a good peace for Ukraine, the war continues and then Trump tries to forget about it all and pretend it never happened.