By the same token, it was this very same lack of early preparation for the Mafia life that made it more difficult for Michael to adjust to it from an emotional & temperamental standpoint, once the time came. Since he hadn't developed the crucial internal sense of balance & discipline that a mob leader needs in order to know when to cut some slack and when to bring the hammer down, Michael increasingly found himself overcompensating in an effort to get his internal bearings - with each new act of ruthlessness requiring even more ruthlessness later, in order to maintain the sense of consistency & order that Michael needed to feel that the family had been protected and was safe.
Don't forget that Michael was also a USMC combat vet. As such, he would have seen death and destruction on a scale his LCN family back home would never have experienced. That coupled with Michael's innate shrewdness really made him, by far, a better choice to succeed Vito than Sonny.
