Haven't they been separated for a while before that? I'm sure they have both moved on to a certain extent. Plus, there were rumors that she was cheating on him. If that was the case, then i'd probably wouldn't want anything to do with her either. But if he was the one cheating, then I'm with you, he would be a dbag.
The media liked to think she was cheating on Orlando with Leonardo DiCaprio but people who saw them together in the club said they were just causally chatting to each other, as Leo knows Orlando. I don't think Miranda would have cheated on Orlando with Leo, as Leo seems to go for women around 24-26, blonde and they never have a child.