But as a larger forward, shouldn't he have learnt how to deal with smaller defenders. I mean it's 90% of his game. As you say he was stronger than Huth and therefore did well, so why can't he do well against weaker defenders? Dawson didn't seem to have an issue against the full back.
see my Huth example. He knows how to use his strength but what does he do when that doesn't work? It's what you are taught in martial arts such as judo. To use an opponents weight and power Against them. In this case rather than throwing them to the floor, all the defender needs is to throw the attacker off enough to either make a mistake or win the ball which is easier with taller players as they have a higher centre of gravity..
As a strong attacker playing target man you get two choices. back off and make space to turn like a smaller player would but that allows the defender into you and forces you forward, not good if it's a high ball as you need to stay where you are, or stand your ground and fight them, problem is that a good smaller defender that has your back will win most of those fights. So you try to draw the foul. Secret option 3 is play in behind but only works if you are faster than the defender which when they are smaller isn't always possible and relies on poor cover which wasn't the case against Utd.
On his own it's a losing fight as the smaller guy behind you can be much more physical and get away with it in comparison to the attacker if the best option is to flood them with bodies in an attacking sense as they can't mark every one. However this is a bad idea in terms of general play.
I'd also mention that a centre back and a full back defend in very different ways, so it's not surprising that Dawson was successful against his man.