MINOR SPOILERS FOR SAN ANDREAS AND GTA V BELOW

As of 1992, even if the player doesn't follow through on the Gang War optional missions, Grove Street has very effectively asserted it's dominance on Los Santos, having either made peace with or thoroughly thrashed every other criminal outfit in town, broken the back of the corrupt elements of the LSPD, and in CJ has both a battle-hardened charismatic leader and massive resources, including multiple streams of legitimate and illegitimate funding, friendly relations with larger criminal syndicates, and contacts with the CIA. If the player does pursue the Gang War, they can literally crush every opposing gang, until there's nothing left but Green on the map...

And then in the 2010s, you find Grove Street swarming with Ballas. None of the 1990s GSF leadership is anywhere to be seen, and there is no trace of GSF activity, even though the Ballas and the Vatos are still hanging in there.

20 years is plenty of time for things to go to hell, but what exactly happened?