You can just break it down by logistics. Likely, Meech and them used highly connected middle men, who sourced product through different groups, and never sat down with the owners in Culiacan. The the only major players in LA at the time were Sinaloa, and Arellano Felix. Gulf Cartels routes run through Texas, and that's it. Beltran Leyva were still with Chapo and Mayo at the time, Zetas weren't formed and don't ship through LA, Juarez doesn't ship to LA, just middle Texas.
Sinaloa and Arellano Felix were the only ones in LA at the time, with the pull to do 100 kilo shipments every month.