The most likely answer is that he had a slam-dunk conviction on the prostitution rap because he was able to coerce several prostitutes and other witnesses into testifying against Luciano. Much easier than trying to nail him on drugs. Luciano didn't help himself by agreeing to testify.

Ntra la porta tua lu sangu � sparsu,
E nun me mporta si ce muoru accisu...
E s'iddu muoru e vaju mparadisu
Si nun ce truovo a ttia, mancu ce trasu.