Height, reach, awkward style, good head movement, fast feet, fast punches that hurt.
If you are in the 1% good enough to overcome all of that and get some clean punches in on him, he will then tie you up and use his weight to lean on you every time you try it.
If you are in the 0.1% good enough and powerful enough to overcome that too and you put him down, he's getting back up.
This is why many believe Fury cannot be beaten and is one of the best ever. Hard to disagree with surely?