How come all of a sudden Juan Manuel Marquez is seen as an easy fight?

You are pretty much on the money here. Diego Corrales was 33-0 when Floyd stepped in the ring with him. Afterward people never saw Corrales as elite...although he was top 10 pound for pound. Ricky Hatton was 43-0 when Floyd took him apart, but afterward everyone thought of him as overrated. Marquez was #2 fighting a Floyd who had not fought for almost 2 years...and afterward (because of Floyd's performance) Marquez is now percieved as easy. Floyd ruins guys. But instead of giving him his credit, detractors would rather say he fights nobodies.