Sollozzo had surmised in just their phone conversations that Tom was keen for the narcotics business before witnessing Sonny was hot for his deal

If Vito had said yes they would have got everything set up and then killed him

Vito's politicians would go over to the highest bidder as more than anything it was always the money
Sonny, with his temper couldn't cultivate or retain them for all the nickels and dimes in Vito's pocket