Vito's modus operandi and shrewd strategy got him to be the top Mafia Don

among others -

• Vito having two separate Capo regime Clemenza and Tessio which on the surface looked like his muscle was half strength than it really was
• The other Dons mistakenly believing Vito was under muscled compared to them
• Vito had the foresight to cultivate political / Police contacts [though Sollozzo had the New York Police Captain in his pocket!]

How come the other Dons couldn't even wet their beak!