I don't want to excuse the problem, but thankfully it's not all Republican supporters who've given in. Cavuto is representative of a broader trend that we've seen in the media and the general public (including in this forum): basically, Trump's balloon has popped for some American conservatives. They saw Trump kissing Putin's ass and realized that concerns about Trump's entanglements with Russia (or just overall softness) weren't just a fantasy. Hell, we saw Trump drop to 44 percent approval in Rasmussen's polling, and that's a conservative-leaning poll.
The issue, of course, is that many Trump supporters are still incredibly irrational; they can stare evidence in the face and still cling to the lie. And of course, many of them won't even look at actual footage and will instead wait for Fox News (particularly Hannity et. al.) to tell them how to think. I look at this as Trump's cult of personality starting to crumble in earnest, but not a decisive blow that ultimately leads to his downfall.