Because beliefs affect identity but its at a different logical level. So cant change the belief because "then who am I anymore?"
Oh when you fiddle with the underlying microcode in someone's brain that "who I am anymore" is an entry point for a whole new personality operating system. One you get to control, and one that can have all sorts of subtle back-doors for future ideas to be planted.....
Very complicated very quickly. For extra-fun points write a meme that scans for certain backdoors installed in people, then come up with ways to exploit those.......