If God Really Exists Why Do Bad Things Happen to Good People?

I certainly don't know, but here is an answer based on the supposition that God exists:

It is that certain bad things that happen, what are often called evils, are necessary evils. That means that without these evils certain good things could not exist, and that these good things are worth these evils so that it is better for these good things to exist even if the evil things also exist, than for the good things (and of course the evil things) not to exist.

You know how sometimes you are willing to accept a necessary evil because you believe that only that way can you have a good thing whose goodness is worth the bad thing? For instance, suppose your dentist tells you that you need a root canal procedure. Not a pleasant thing. But you have it done anyway because unless you do you will have greater trouble. So you have this unpleasant procedure for the sake of a healthy mouth. You accept an evil because it is a necessary evil. Now, let's apply this to the question. We all believe that compassion for people in trouble or in need is a good thing, don't we? On the other hand, isn't it true that for there to be compassion, there have to be people in trouble, perhaps very ill? You could not be compassionate about nothing! So, according to this answer, certain kinds of evils exist for the sake of the compassion which is good.