His "white supremacy = omnipotent villain" gimmick got tired and ran its course. So he had to create a new bogey man . This new bogeyman is easier to sell , actually.
Whereas most people know white people VERY well...because of history,past experiences, and living in a country where they control most of the institutions............people who didn't grow up with Africans or Islanders know very little about them. You can convince your audience anything about people they don't interact with. Hey, those people are that way and here is what they secretly think / say about you.
Also, convincing an individual with self hatred & low self esteem to hate a person who looks like him is easy.