Most of the cast have some grievances with Shatner over shit he did during StarTrek TOS. On the other hand, he had nothing to do with the distribution of money or royalties from Star Trek. In fact, Shatner was living in his car at one point after the show was canceled. None of them got paid much at first. Shatner's worth probably has a lot to do with all the other roles he had besides Star Trek. Nimoy and Shatner probably had the most work outside of the Trek Universe.
Sadly while Star Trek was a groundbreaking show, Hollywood was still Hollywood, and roles for women of color were still scarce in the 1970s compared to today. Nichelle Nichols has only 69 entries in IMDB, while Shatner has 249. He also has numerous producer and director credits. White male privilege isn't just a theory.
My favorite story about how cutthroat The TV and Movie world is concerning Star Trek is the story behind Star Trek the Animated series. The producers of that show only wanted Nimoy and Shatner. They were going to use regular voice-over talent for the rest of the cast until Nimoy put his foot down and threatened to leave the project if they didn't bring in the rest of the crew.
RIP