RFK Jr, like the other third party candidates, is running as a spoiler to help Trump — his staff have even said so:
The only way that Trump can even, remote possibility of taking New York is if Bobby is on the ballot. If it’s Trump vs. Biden, Biden wins. Biden wins six days, seven days a week. With Bobby in the mix, anything can happen
I have a family member, who have always been republicans (voted for Trump both times) who went down the ‘Bret Weinstein’ anti-vax path, and is now a RFK supporter. Anyone who listens to that podcast are likely supporters of RFK. Many Joe Rogan listeners as well, since he pushed a lot of anti-vax shit.