In my view, one of the things about the Michael Corleone character that makes him so fascinating is his complexity and his contradictions.

In some ways, having been groomed for an entirely different type of life prior to his ascendance to the donship, actually made Michael more effective than he might have been, had he been raised to succeed Don Vito, as Santino had been. He was more sophisticated, more cosmopolitan, and certainly more educated than the typical Mafia don. That allowed him to think outside of the box, be more creative & entrepreneurial, and ultimately to act on new opportunities for the benefit of the family business that might never have occurred to the old-school mobsters.

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.

Because Michael had been raised with the expectation that he would lead a law-abiding, respectable life, this expectation became a core part of his being - from a much younger age than he was when he became the new Don Corleone. Through all the changes of the ensuing years, it remained one of his few remaining links to the person he once was. The fact that he continued to cling to it ever more compulsively - even as the circumstances of his life dragged him ever farther & farther away from it - explains much of the psychological basis for Michael's growing sense of desperation to become "legitimate". Ultimately, I believe he would have done almost anything to "rescue" that good-natured, idealistic boy who was still (barely) alive deep within him - and save him from being snuffed out entirely.