My in-kayfabe explanation for when stuff like that happens to giant wrestlers is that they are so not used to being dropped on their backs like that it serves as an Achilles Heel for them, hurting more than those that have had it happen to them often.
Like the bigger they are, the harder they fallβ¦but they donβt fall a lot.
That was pretty much the case with Andre too. The minute Hogan knocked him down once he was out