I think quidnunc is right. I just got the digital edition of National Review, and his regular "happy warrior" column is in there, but you can tell it was written before he went on hiatus.
Is this hiatus just a well earned vacation? I'm a little concerned that his site say "family and personal reasons". IN my experience that's never good, and does seem to be more than a vacation. Hopefully Mark and his family are OK.
As we read in the article, Mark Steyn mentioned that he sought treatment for a medical problem this summer. Perhaps the problem is on-going. Hopefully, it will be resolved with a good outcome since he is not dependent on socialized medicine in New Hampshire.