Their arrival occurred during a surge in popularity of hip hop in the United States, which allowed them to participate. Salvadoran hip hop is still a smaller kind of music but it is an important part to communities and the lives of many Salvadorans.
This passage describes how the arrival of this group coincided with the rise of hip hop's popularity in the United States, allowing them to participate in the scene.  Despite its smaller scale, Salvadoran hip hop remains a vital part of communities and the lives of many Salvadorans.