I mean, he's RFK Jr. He's always been around and has always been able to get publicity when he wants it. Like most of the next generation Kennedy's, Junior went through a pot and heroin phase, but he spent most of his adulthood as one of the leading environmental lawyers and activists in the country. He was a good speaker and a good writer, just not on news sources you might frequent.
He became an anti-vaxxer well before COVID, and started making the news about a decade ago as a famous anti-vaxxer who brought the Kennedy halo to a discredited cause.. He also went off the rails revisiting his father's assassination and has absolved Sirhan Sirhan of the crime citing a deeper conspiracy (although Sihran himself had confessed long ago). The Kennedy family, which actually isn't that bats#!t, has been distancing themselves from RFK for several years now. He's an embarrassment, but given a little spotlight and encouragement from his historic detractors, he's branching out into other conspiracies.
Now that he's running for President, Republicans have latched on to RFKs anti-Vax, anti-Facui, conspiracy-happy crusades and would love to see him drain support from Biden. Didn't someone suggest both Biden and Trump could pick RFK Jr. in this very thread? That's nuts.
Conservatives who purport to love RFK Jr. for speaking harsh truths should know he's also way into Alexandria Ocasio-Cortez's Green New Deal, and opposes the current distribution of wealth to the elites.