Because Hugh Hewitt asked him. It's in the article.
Why Hugh Hewitt would ask him, I have no idea. :)
Just because he asked doesn’t mean he has to answer in that way. Hewitt was trying to get Trump to say something stupid and he took the bait. He should have answered that the couple are not relevant and we’ve got huge problems in this country to tackle. He should have called Hewitt out on such a stupid question.