Why isn’t antes de or antes de que used?

“podrás ver antes que nadie” Initially I was wondering why antes que is used here instead of antes de, but after doing some research it seems que might be replacing de to signify the change in subject from tu to nadie. Or is it because antes is acting as an adverb here within a fixed expression “poder que” rather than as a preposition?  Also wondering why it can’t be antes de que, but I’m thinking this can only be used to introduce a subordinate clause such as Puedes hacer esto antes de que nadie lo haga? Could you please provide some guidance? Thanks in advance!