Wasn't Nas talking all that street shyt, mafioso bla bla when he never was a G in first place? Then all that baller shyt, Oochie wally and on. Most rappers, almost all rappers "dumbed down" their sound, sometimes to make better music or sometimes times to sell more records. Some rappers can't dumb down their music, they don't know how to make hits. People give them cred but these dudes might not be able to make hits, that's a lot harder than making 'socially conscious' music.
People listening to metal are probably a lot smarter on average than people listening to conscious rap. I don't know how the spread is between conscious rap and ignorant rap though, but to think that conscious rap makes people smarter is just stupid. Why? Cause most of these rapper are not even half as smarter as an half ass high school teacher. Structural and social improvement is the only thing that can improve our wellbeing not some fukking dumb smart rapper.