I think the schadenfreude component of much humor is overestimated. I believe our laughter in response to another's misfortune is less often a result of any genuine appreciation of ours for their misfortune, and more often a sudden and involuntary outbreak of relief at our own safety; that we were in this instance spared. Possibly magnified by our recognition that we've been in situations where we exposed ourselves to the risk of quite similar misfortune, just as stupidly, and lucked out or through - a reinforcement that carries a lesson with it: maybe this recognition will help steer us clearer in the future. Or maybe a touch ruefully, we realize it probably won't. That we'll be caught and tripped ourselves, and look a fool, and others will laugh, but we'll carry on through.
The absurdity of our bravery, and the probable futility of it, makes us laugh. I think it is a sympathetic response more than it is a sadistic one.