ms-13 started after all the people from el salvador started arriving in the late 1980's
during and after their civil war
they pushed out the others because they were more ruthless not because they were engineered
they were more visible by the 2000's after spreading through the prison systems
i would be more inclined to think the crips and bloods were engineered to sell the cia drugs after they wiped out the original italian mobs
the black gangs were more easily controled than the el salvadorions