Ukraine would have quickly crumbled without the aid of all NATO countries. It's highly doubtful that Trump would have corralled their cooperation and contributed to their defense in the same way Biden has. I also dont believe he would have gone all in on the crushing sanctions we applied. Ukrainians are badass fighters but you're kidding yourself if you believe they stood a chance without the assistance we provided.
But they would have not gone down 'without a fight' as you said. And I don't know that Russia would have had the success you think they would have.
Militarily, Russia is a bad joke. They are nobody to fear (UNLESS they get real chummy with China - then we have a freaking problem). Their gear is pretty terrible too. The T-90 has a fine gun but against the newest Abrams, Challenger, Leopard, or that new South Korean thing (probably the best of the lot) it doesn't stand a chance in hell. Think Shermans vs Tiger tanks, but with a lot more Tigers.
And their infantry, to a man, is pretty bad as well.
@PawsFan_ went into that before.
And fighting an enemy on their own turf is very, very hard to do. See the American Revolution, American Civil War, WWII's eastern front, Russia in Afghanistan, the US in Vietnam... They know the area. They have the sympathies of the local population. The invaders don't.
(I would say the US in Afghanistan but we basically just gave it back to the Taliban so that doesn't count, plus we can project power like nobody else anyway).
I don't much care what Trump would or would not have done anyway, because he's not the standard we should hold any elected official to. Neither is Biden.
If you can neutralize Russia's nukes pre-launch (and I don't know HTF to do that) then you can pretty much castrate the 'Russian Bear.'