It is a confusing statement. I understood it to be basically that once he is guaranteed to be president, Putin will know his man on the inside will be in charge, and Putin can end the war/negotiate for favorable terms with the US as enforcer.

Trump can’t end it before the election, because there’s no guarantee he’ll win.

Trump thinks that makes him a brilliant negotiator, instead of what he really is which is a stooge that can be played like a fiddle.