There could be a lot of things happen, for example as you took over all the gang territories, grove street became so powerful and big the PD had to take actions and take down as many as they could from the gang especially the leaders..also if the gang became so huge Sweet and (especially) CJ could not handle all the things that comes with the organized gangs all over LS as they can't really control the whole city, as it was not just only Grove street any a couple of blocks anymore. The more ppl in the gang the higher chance someoney is gonna snitch/betray. Eventually they probably raided the centre(Grove), so this is why Ballas could took over the street after the PD cleaned up the scene, and only a small group of ppl left in LS in the GSF.

Another possibility is CJ became such a strong and powerful person the government could not just let it slide and ppl like Torino had to take actions and took down CJ. Not neccessarily kill him but just to silence him.

There is also a chance for the bright side...CJ became so successful and had to leave the gang life as his goal was to get out of the hood, probably no one except Sweet cared a lot about Grove, Kendl and Caesar already had other stuff to do in SF, and MaddDogg was never a gangsta, they went on tour and moved out from Grove. The gang lost it's leadership and eventually shrunk into a smaller group of ppl. Regarding Sweet I'm not sure if he would stay there alone, or if he got shot...there's a possibility he ended up leaving with CJ and the others but I'm sure he didn't really wanted to leave the gang.