Why murder the man you just asked to provide you with something that you cannot provide yourself if you believe that such provision is essential to your efforts?
That was my original contention. On the other hand, Vito's refusal meant that Sol could not do business. He either had to retreat with his tail between his legs, or do something else. Killing Vito and then hondling with Sonny and Tom may not seem logical to us, but I suppose Sol and his supporters felt it was preferable to his simply going back to Turkey or Sicily.
