Instead, Trump and many other Republicans seem to feel ideological sympathies with Putin’s version of right-wing authoritarian nationalism.

It might be much, much simpler than that.

Trump and Republicans have a lot of conspiracy theories about Ukraine that long predate the invasion. They're convinced that Biden cooked things with Ukraine to help Hunter, they're annoyed that Trump was rebuffed by Zelenskyy in his efforts to get material to use against President Biden.

Remember the first Trump impeachment? The one that was supposedly going to mark his place in history, and which was ground entirely on dealings with Ukraine? Yeah, me neither, most of the time - it's pretty much gone down the memory hole. But Trump had a grudge against Ukraine - and has been convinced that they're not on "Team Trump" - for years before the invasion. And he's propagated that to the party. The "many other Republicans" are probably not sympathetic to Putin's version of authoritarian nationalism, but are very unsympathetic to Ukraine and Zelenskyy.