Some of them are no doubt serious; I seem to remember a study showing that mathematicians are more likely to be theist than atheist.
In my experience, "Why did God pick X?" and the like is shorthand for, "Is there a classification/uniqueness theorem that says X is the only possible solution to the problem?", which is how it is used here.
Again, thanks for drawing out the shorthand. I personally prefer reading the "is there a classification/uniqueness theorem that says..." over "why did God choose to...". It requires zero cycles to process the intent of the first version, while the second makes me stop each time and wonder which one the author means.
In my experience, "Why did God pick X?" and the like is shorthand for, "Is there a classification/uniqueness theorem that says X is the only possible solution to the problem?", which is how it is used here.