Trump told everybody that he was solving the Ukraine thing or whatever and that Putin respects him or something, and then Putin sent a couple of massive drone raids at Kyiv and elsewhere, and then violated NATO airspace with Russian MiGs, making Trump look weak, all the while Trump is campaigning for the Nobel Peace Prize by doing things like stopping the war between Armenia and Cambodia. On top of that, European politicians are one-upping Trump and looking like bad-asses and telling Russia to STFU and don't come whining when their fighters go missing.
Trump does not like to look weak, especially with so much shit going down (being mocked over the National Guard stuff, Congress still looking at Epstein stuff, etc.).
And let's be real - if we opened up the spigot and things really started flowing to Ukraine, and they make a lot of progress towards Russia and even remove Russia from large parts of the conquered areas, Trump will look like a genius and call himself the savior of Europe.