To be cool as a successful hip hop artist you had to make pop come to you, not the other way around.
"It might blow up, but it won't go pop" was De La Soul's Buhloone Mindstate mantra, and it was a wider statement of confidence in hip-hop's ability to make the mainstream see its vision for the future. Hip-hop built it, and they came. R&B swiped hip-hop's breakbeats and attitude, then its language and slang; soon rap guest spots were di rigeur. The Chronic redefined pop music, and what could make a hit. Then, by the late 1990s and early 2000s, the genre's mainstream had become the pop mainstream. Rappers from across the country were the mainstream stars, and the country's dominant sound was hip-hop; clubs didn't play anything else. Top 40 radio consisted of hip-hop, and R&B/teenpop influenced by hip-hop producers.
Today, hip-hop artists rarely touch the charts without a Drake hook or a house beat. Even Wiz Khalifa's biggest singles relied heavily on European pop producers Stargate. Pop music's sound shifted towards dance in the mid-2000s, and rappers could either embrace it (like will.i.am and Flo Rida), try to divide their styles between the two genres (like Nicki Minaj's schizophrenic Roman's Revenge) or marginalize themselves from pop altogether. Hip-hop is no longer the vanguard; it blew up, and popped.