I have difficulty understanding that any intelligent person believes in God. However, I know that many do, whether or not I understand it. My failure to understand what's going on inside other people's heads is my problem, not theirs. I try my best not to take my lack of understanding and use it as a projection of what other people "really" believe.
If someone says they believe something, do them the courtesy of accepting that they actually do believe it, unless you have very good reason to think otherwise.