In the 1980s the opium come on sicily from Turkey and was transformed in heroin and distributed in america and europe. The sicilians lost the monopoly on heroin because the italian state hitted hard the drug traffickers and the drug labs in sicily and the coke slowly replaced heroin as more profitabe drug.
Plus in the late 1980s the mafia both in sicily and the USA was decimated by rats and killings and the american cousins decided to split by her cousins 'cause Riina violence.
While the chinese mafia was more tight and efficient.