Unlike Joe Biden, who's portrayed as having stepped down when really he was forced out, Kennedy has sincerely sacrificed his political ambitions to serve a greater cause: kicking the Democrats out of the White House. While it's not clear how this will affect the election, many of his supporters have said they'll vote for Trump if he drops out. Kennedy and Trump disagree on many things, but they agree on enough to join hands and defeat the warmongering Democrats.
Kennedy has just added to his long list of deranged political decisions. First and foremost, he believes he has enough supporters to help Trump, which is unlikely given his plummeting pole numbers and recent negative press. To make things worse, he followed the announcement by pushing conspiracies about the food industry causing mental health issues. With Kennedy's endorsement, Trump can lose this election with even more embarrassment.