Why did FFC and Paramount make a familial mafia head rather than a familial businessman or politician? If Vito is a businessman or politician, will the movie attract the same amount of attention? Certainly not.
The two most important point that made Godfather Trilogy successful are that it was a mafia movie and that its hero was 'kind' and 'good' on strange terms.
So I believe FFC and Paramount took advantage of our curiosity as to mob life and goo-bad man to sell the movie series, at least to some degree.
Then the conclusion may be that Godfather Trilogy is a little misleading and against the moral of the society.
Just a thought, you opinions?