In this, trump’s acting in the same way he did in his first term. He believes and promotes the opinions of the last person who spoke to him. Thus time Starmer was that person, and he’s been trying to get trump to maintain support for Ukraine for a while. This new stance will last until someone else comes along and persuades him otherwise. I would expect to see various E.U. leaders falling over themselves to say how great trump is for restarting support to avoid this happening.