The dumbest questions I've ever been asked and continue to be asked are by my mother, and they always begin with, "Why do you think they did that?" It could be anywhere from, "Why do you think they painted their front door black" to "Why do you think they planted azaleas instead of roses."
Bless her heart, she feels people should think the way she does and make decisions the way she does. I've finally told her that I will not be able to answer, to her satisfaction, any questions that begin with "Why do you think they......"