Because he totally called yesterday's Drudge-Hannity-whatever idiocy a couple of weeks ago. He explained why it's important for Mitt Romney's campaign to keep generating stupid junk to throw at Barack Obama, because if they don't...
It's vitally important for, say, the Romney campaign to keep the movement-conservative audience engaged, to keep their interest up so they will turn out to vote in big numbers.
But it's also important that the movement-conservative marketplace not go veering off into dangerous looney-land. And that's really, really likely if you're not feeding that beast. If you're not giving them something reasonably safe to be outraged about, they're likely to go looking for outrages in, say, the latest press releases from the Gun Owners' Action League, or the latest book from Regnery, or worse.
Which is, more or less, what I think happened yesterday. I could be wrong, but I don't think the Romney campaign wanted to occupy the pre-debate hours with this one. The Biden thingy, yeah (and I'm not explaining what any of these are; if you don't know, you're better off anyway). But ancient news that was guaranteed to leave a sour taste in the mouths of pretty much everyone outside of the conservative closed information feedback loop? I really doubt it.
And yet: as my brother, the keen observer of this stuff, said: if Team Romney doesn't act aggressively to program the Republican-aligned media, then they're going to find something else to run with, and it's apt to be a mess. So by this standard, even if junk like "build it" don't actually work, they might still be a successful way of keeping the GOP partisan press busy so they don't do something even worse.