Im sitting here drinking coffee at a cafe. Was reading our local science magazine. It said that T.rex danced during mating. The problem though when you way so much is the pressure on the feet.
Thats why I believe such a predator hunted on soft grounds. Maybe it seeked those almost dried up lakes with soft sand. Because the ground is difficult to move in the T.rex got the upper hand on the pray. Who could not move that fast in the mud or soft sand.