I don't think god makes mistakes but when the people wanted a king, god pretty well let them make their own way in life.
An example of the fact that mistakes happen and god isn't behind it can be found here
http://www.chm.bris.ac.uk/motm/thalidomide/first.html. I only provided one link but googling Thalidomide will return many items on the subject. This was something that happened when I was young and everybody my age or older would know about it. It is pretty much forgotten today and this is why drugs receive very careful testing before being released to the public.
They have found other things Thalidomide is good for and the drug is on the market for some very special conditions, but I am sure there is a very specific warning label on it to prevent this from happening again.