Why would it come as a surprise that atheists and agnostics would do better in such test? The answer is quite simple, because we're skeptics and we raise questions and seek the actual answer instead of just accepting something to be true without evidence. If you're a man of faith in the god from the bible you have already then accepted that there is one answer for some of the biggest questions about life, the universe and our existence, accepting it without any reasonable explanation at all. A man who accept unreasonable answers as such as god created everything, has neither need nor desire to seek the truth because he truly believe that he already does know the truth. But the fact that so many people with faith know so little about what they actually believe in, is a shame.
Let's say that there is actually a god, do you think he would be pleased about this? Don't you think he would wan't to see human kind actually use the extraordinary gifts he gave us? Why would he give us such great abilities and expect us to limit ourselves to use those abilities?