I agree that after the information about McCluskey came out, the police made sure that Vito had the protection he needed. Remember during the war, the police were cracking down on all kinds of "business" operations to which they usually turned a blind eye, and that was hurting everyone's business. Barzini and the others, as Sol said. missed their chance. Besides, everyone knew how infirm Vito was, and that Sonny was more likely to do something stupid to lose the war.

This thread raises another question. How important was Solozzo in the scheme of things? I think Barzini was leading the charge to get the families into the drug business, and Solozzo happened to be in the right place at the right time. N.B. when Vito caved after Sonny's death they made a deal on drug distribution, and Sol was long gone.

Sol turns out to be a stalkiing horse for Barzini.