I think they killed Furio's story line when they wrote him off the show. As I understand it, the actor was leaking spoilers and they found out. The boss David Chase whacked people quick for that.

"...the successful annihilation of organized crime's subculture in America would rock the 'legitimate' world's foundation, which would ultimately force fundamental social changes and redistributions of wealth and power in this country. Meyer Lansky's dream was to bond the two worlds together so that one could not survive without the other." - Dan E. Moldea