The cross of Cohen is all over the place and to no apparent purpose. 

Like what is the purpose as the lawyer for Trump of this?

A lawyer should have certain points that he wants to make on cross examination. One very fine local Miami lawyer had a personal rule that every point you want to make should be on one sheet of paper, only one. You can go with the flow from there but you can't neglect those points. Blanche had Cohen's ownership of Trump properties on his list of points to make. For reasons known only to him.