My personal belief is that this entire recent iteration of the beef between Russia and the US kicked off because of the Magnitsky Act, which was entirely created by Bill Browder's testimony and at least partly from the US congress's genuine concern over the human rights issues involved, i.e. very little to do directly with anything geopolitical. I don't think the intent was to go all the way to hot proxy war and active democracy-undermining conflict with them, but we definitely didn't react "oh dead lawyer who GAF" even back then when it was a much smaller deal.
all they get is stern warnings
You are aware that Russia is excluded from most international forums big and small and under heavy sanctions currently and that we're sending (or were sending until a few months back) tons of high-powered weapons to Ukraine to use to blow their soldiers up, yes? And that we just enacted a whole bunch more sanctions specifically because of Navalny?
That's a far more likely contributor than Trump's comments.
Personally, my initial reaction was actually inclined to agree with you on this part. I have trouble seeing how anything Trump says would have anything to do with what they did to Navalny. On the other hand, Vindman has a lot more familiarity with Russia's operating principles than either of us; he's from the USSR and spent significant time in the US diplomatic corps and professional study of the topic, so I'm a little reluctant to just airily dismiss what he has to say about it. He's much more qualified than you or I are on it so I'm more inclined to hear him out.