What did Ali's pulling have to do with speed or agility? Foreman couldn't break free from Ali's clinches, so where was his strength advantage? The strength in Ali's arms was enough to neutralize Foreman for a big part and also drain him of his energy.
Ali's stamina beat Foreman and that is the cold hard truth. He outlasted him. Like I said strength means nothing if you don't have the stamina to back it up.