In the classic Doctor Who story Genesis of the Daleks we see Davros, the evil genius who creates the Daleks. He taught his creations that they are the superior race of the Universe, and to hate and destroy all lesser races. Naturally, since Davros wasn’t a Dalek, they reasoned that he was an inferior, and exterminated him.
I think a similar fate awaits Voldemort. He hates mudbloods - people born of non-magical parents. But Voldemort’s father was a muggle. So, his followers will embrace his ideas and seek to destroy all mudbloods, but that includes Voldemort himself.
Nah, his underlings are scared poopless of him. They aren’t some sort of uber-man Waffen-SS types, kicking ass and taking names, they are sort of evil keystone cops that get the fight taken to them by a bunch of kids.
If the ‘Death Eaters’ were more competent in the books, sure, I could see the possibility of a coup. Keep the revolution pure, as it were. But from those bumblef*cks? Nah.