I had this thought as well, particularly regarding Survivor. His address didn't overwrite Survivor like other similar things have; I think I can remember Obama having addresses that just cut out the portion of the show that overlapped. In this case, though, Survivor was paused until after the address, so nothing was lost.

With that in mind, I'm wondering how many non-politically minded households just left it running rather than skipping it, and actually heard what he said. Most of his address was a recap of the prior year, and things that might be obvious to those who pay attention, but aren't things that the non-political would really know about.

Not only that, but he could have done this at any time, for the message that he gave. However, with it taking place mid-way through Survivor's season finale, it seems like he'd have a higher audience count than he would have had otherwise, even if most skipped it.