Because every other Democrat thinks that parroting insane conspiracy theories is disqualifying. And asking honestly, even if Kennedy's other policies were standard Democrat fare, what about him is better than Biden ?? How is this less baggage ??
A great example of conspiracy theories being disqualifying for dems is how nobody took Marianne Williamson seriously once all the "healing crystals" stuff hit the fan. And afaik, that was the only conspiracy-adjacent thing she espoused. For the republican party, believing in conspiracy is a requirement. The crazier, the better. I had to look up RFK's policies, because he never talks about them. They're relatively democrat-centrist, from what I can find. Some even sound progressive. But all he talks about are conspiracies. THAT is republican. And so is being "anti-war" while also advocating to bomb and/or invade Mexico. I'd love to hear RFK Jr. be asked that question. I can add legit source links to this thread all day. We can't just watch the candidates lie to us in debates or interviews and trust everyone on the basis of how charismatic they are.