I personally think that the fact Floyd was a lot bigger and stronger definitely had an effect. If he would have drained himself too much then it's possible Marquez would've decisively beaten him, AKA Manny V Oscar, but I'm not saying Floyd being completely drained like that would've been in any way fair nor am I condoning it. Marquez was a shell of himself whereas Floyd was strong and fit, at that weight. The fight would've been closer if they did meet at a smaller weight even if Floyd was in his prime. It woulda been more Mayweather/Castillo than what we witnessed in Floyd/JMM ...
Floyd has ALL the advantage in the fight: height, reach, PLUS the wide SIZE difference. Add up Floyd's better boxing skills, and you have a SHUTOUT. Floyd cherrypicking a small boxer 2 division below him is $%^&*!