Q: If the the main purpose of the Turk approaching Vito was to get the political protection needed to allow the drug business to function, why would the Turk sink his own ship by asassinating Vito and severing Vito's "political contacts"?
The Turk may not have know that he potentially sunk his own ship when trying to kill Vito. At that meeting between The Turk and Vito, Sonny showed his hand by speaking out of turn. Sonny showed that he was, as Sollozzo puts it, " Hot for my deal." And at that moment of Sonny's outburst, Sollozzo
thought that by getting Vito out of the way, Sonny would eventually come around and go for his deal. And in thinking so, Sollozzo probably figured that being Sonny was the second in command of the Corleone family, and the Don's son, that he, Sonny, would retain those political contacts that could be used in this drug deal.
So basically Sollozzo probably
ASSUMED that Sonny would still have access to the politicians that Vito had in his pocket.
Sollozzo had no way of knowing that without Vito, the Corleones would lose their political contacts. As far as Sollozzo knew, it was the Corleone's who had all of those political contacts, and not specifically Vito.
Don Cardi