>>...this decision is simply to spite Trump and make it as difficult for him as possible to make a deal between Ukraine and Russia
Among other things, it's a gift to Trump. It gives Trump a lever in upcoming negotiations; it changes the 'stick' of "if you don't do X I will allow Ukrane to do Y with our weapons" to the 'carrot' of "If you do X I wil stop allowing Ukraine to do Y'.
Surprised you couldn't see this.