True Lana from what was seen in the movie, Barzini was the only contender, younger, ambitious and impatient but was no match for Vito

It was the right time and right place, perfect times and opportunity / need - killing tyrant Fanucci, earned Vito his formidable reputation Murder, extortion, threat of lethal violence, comply or die "for justice, we must go to Don Corleone."