Back in the early 1990s (when I was a university student), I read an article (or perhaps it was a documentary)that discussed about how both MLK and RFK were planning a large demonstration like the 1963 Million Man March that was going to be for getting the United States out of Vietnam and also for black rights. Apparently many establishment Dems like LBJ and others and their friends in the FBI saw this planned demonstration as a threat and acting on this threat was a likely theory as to why both men were shot dead within the space of two months.
Martin Luther King worked against the political establishment.
The politicians like to talk about his non-violence to distract from the fact that he was a thorn in their side.
What they felt they had to do to deal with him is a mystery clouded by all the FBI files on MLK hidden.
Trump actually got one FBI report on King out this year with all the JFK files released.