Trump makes deals. He's a businessman. Thats what he does. He's running the U.S. like a business, right?
One problem: Ukraine isn't his to barter with Putin.
He doesn't have to face the repercussions if Russia reneges on the deal and continues to attack Ukraine. Additionally, his posturing about using military and economy force to annex other countries (rhetoric or not) sends a loud message across the world that the Great Game is back on in full force.
You'll see China make a move for Taiwan. You'll see Pakistan and India finally settle scores in Kashmir. Iran will have nothing left to lose in the Middle East. It won't end.
In "The Art of the Deal", he speaks heavily about leverage being the one thing you never negotiate without. In Ukraine, he has no leverage that is discernable to negotiate a peace; only the ability to give concessions to try and appease Putin.