A lot of misinformation here. Discredit this bit by bit. For hip hop NOT to be mainstream until 1993, that means MC Hammer wouldn't have gone DIAMOND in 1990 or Vanilla Ice going 9 times platinum that year. What you are confusing is hardcore rap didn't hit mainstream airwaves until The Chronic. But commercial rap was indeed mainstream. Kid & Play's House Party blew up and they had a cartoon. Fresh Prince of Bel Air was a major hit. And then there's of course MC Hammer who was literally competing against Michael Jackson who was still in his prime. MTV literally have a video battle debut between 2 Legit 2 Quit versus Black & White where people could call in to pick who had the better video. To say hip hop wasn't mainstream in '93 is absurd. I could give you countless examples of how that's incorrect.
Saying hip hop didn't have a Grammy category until 1996 is ever more wrong and shows your own ignorance into hip hop history. The FIRST HIP HOP GRAMMY CATEGORY EVER was presented in the year 1988! It was for BEST RAP ARTIST OR GROUP. DJ Jazzy Jeff & the Fresh Prince were the winners, but they BOYCOTTED along with all of the hip hop artists with the exception of JJ FAD because the category wasn't going to be televised. Yo! MTV Raps even had a boycott party episode special hosted by the aforementioned Jazzy Jeff & Fresh Prince.
The NWA part is partially true but also a bit inaccurate, Straight Outta Compton had a full RADIO EDIT album for the album specifically for radio play. It was played on radio, but during the time of 1988 when hip hop WAS not commercial, most rap songs were played very late at time no black radio stations, and most of those radio stations were still mom & pop. Radio wasn't like how it is today. The 1996 Telecommunications Act changed the game and consolidated all the small radio stations to large conglomerates such as Clear Channel. NWA went platinum because of the word of mouth and the cease & desist letter by the FBI. Once news hit that MAJOR MEDIA was giving that group free promotion trashing the group and the music which had a reverse effect because teenagers were intrigued about what's the hype about with the album. The FBI letter was the greatest thing to happen for NWA and for gangsta rap as a whole to flourish.
The Chronic album, granted, was one the 1st hardcore record played on MTV outside of Yo! MTV Raps (who incidentally banned NWA). But Yo! MTV Raps wasn't the only televised show. Rap City was around since 1989. Ralph McDaniel's' Video Music Box pioneered it and was still going on. Miami based THE BOX (formally known as the Video Jukebox Network was jumping and pumping out all the underground rap videos. Access to hip hop was bubbling which also help propel the popularity of the culture through many regions.
Lastly, you are out of touch to the HISTORY of hip hop. RUN-DMC & the Beastie Boys were the FIRST RAPPERS to go platinum. SALT & PEPA were the first female group to go platinum. And this was back in the 80's. Rappers long were able to go gold and platinum. The DIFFERENCE IS those records were POP RECORDS. WALK THIS WAY was a POP RECORD. PUSH IT was a POP RECORD. Even ME, MYSELF & I which push DE LA SOUL to go PLATINUM was a POP RECORD and that group used to hate that record because it was a pop record. The hip hop community back in those days DID NOT CARE TO GET PLAQUES, they did it for the love and the respect and their names out there as one of them ones. The record sales were an afterthought, and many got screwed over their deals because of it.
Once The Chronic dropped, it changed everything. Now when major labels were averse to hardcore records, they want their own Chronic album. Many labels sought after the hardcore acts. And it been that way ever since.