Times had changed so much between Vito and Michael.
The area Vito started from and worked almost his whole life were from a time where people knew each other, they lived worked and shopped within a few miles. Don Vito could pull strings in his community. He ran it like a king.
By Michaels time the stage had changed, people had more and moved from the old places. Old friends had moved up and out and new people took their places in the old areas. Times had changes and Michael was no longer big in the old community his father once ran and was so well known for.