Fredo never would have been the Don. Sonny,showing a rare flash of wisdom got Fredo out of the picture by sending him to Las Vegas to Learn the Casino Business. Notice that Fredo did not come back to New York after Sonny's death.
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
