Third party typically helps the democrat party.
Not with RCV. That's the entire point. It lets people support third parties without "helping" either of the majors.

Partisan paranoia is so unhinged that each side thinks RCV is a "trick" by the other side.
Either that, or the partisans recognize that it would change their game. That it would discourage fear-mongering and divisive candidates. And, it turns out, they
like the fear-mongering and divisiveness. It's how they roll. They don't want to give it up.
If by chance the third party candidate does win they always vote with that maga party you claim to hate the democrat party. Secondly third party typically takes votes from the Republican party.
RCV really doesn't bolster third party candidates that much. In most places it's been used, you still end up with two dominant parties. What it changes is the spoiler effect. It does away with th "lesser-of-two-evils" nonsense, and allows voters to actually vote for their favorite candidate without fear that their vote will be "wasted".
What do you think of run-off elections? In some states.(eg Georgia, Louisiana, Texas, etc ...), they won't declare a winner if the candidate with the most votes doesn't have a majority. In that case, they eliminate the lower tier candidates and vote again.
Well, that's all RCV is. It's just streamlined way of doing runoff elections. You essentially pre-vote for the runoffs by ranking the candidates.