What killed San Shou/San Da in the US? It's an interesting question, I can give you a quick summary of some of the issues
Ironically, san shou/san da (let's just say sanshou for now) was first made illegal in NY. The law that made MMA illegal was used to close down pretty much all martial arts events here for almost 2 years.
The two most progressive hubs for Sanshou were NY and San Jose (Cung Le obviously). At the time both NY and San Jose were pushing both amateur sanshou tournaments and starting pro leagues. We both figured it was going to take 3 to 5 years to get pro going.
After doing my third pro event, I found out sanshou was illegal. It took us two years just to get amateur approved, pro is STILL ILLEGAL
The NY commission then hammered us again by closing many venues to us because of illegal MMA fights, ie close down anyplace that can do a martial art event so no one can do an illegal one
IN San Jose, Cung still represented hope to all of us. But it seemed that just as we were pushing the sport forward, those who had once controlled the sport tried to sabatoge us. IE if they couldn't be total dictators and control everything, they'd rather destroy it
I'm not naming any names of course (shawn liu and anthony goh)
Three years in a row the old powers tried to schedule something to conflict with Cung's event. I know it discouraged and tired out all of us, the entire community. Then the legal ban hit in CA.