Organized crime generates revenues in the billions annually. Vito had been in business since the 30s. Michael's adept expansion of the family's enterprises, both legal and illegal, could easily have amassed quite a fortune. Don't forget, Michael is working through a foundation and I am sure he arranged for its funding and disbursements to be done legally.
In addition to In God's Name, you might read God's Banker also.
"Generosity. That was my first mistake." "Experience must be our only guide; reason may mislead us." "Instagram is Twitter for people who can't read."
