This board doesn't seem that friendly to newbies right now, but this touched on what I always felt was a major, perhaps THE major, theme in the films: the struggle to reconcile traditional Sicilian/mafia traditions with changing American realities.

I feel that this is Michael's major failure. He recognizes that times are changing but his attempts to evolve end up isolating him and destroying his family. The caporegime structure was made for simpler times.

In my opinion, the turning point was merely the passing of time and, in particular, the social changes in the post-WWII era.