To elaborate, the rocket can take only about 1 atmosphere of pressure in the radial direction, but much more force in the longitudinal direction. It's designed to withstand the stresses of going in a straight line, but as soon as it bends it'll crumple, like a toilet paper cardboard tube.

So when the thing topples over, it bends. And when it bends, it ruptures because it's far in excess of the loads under standard conditions.