I disagree, I think they did this in order to capture more users. Not everyone uses Twitter. I believe Twitter is shooting for the "everyone" demographic, not just kids, the media/artists and tech-savvy people who got into it "before it was cool". If that is true, that means they are attempting to leverage Google, which everyone's already using, in an attempt to boost their legitimacy as a source of real-time information and get more exposure. Twitter's a media company, after all, so they are looking for more and more exposure whenever they can get it. It wouldn't be surprising to see your strategy implemented at Twitter after this deal has come and gone, if Twitter is playing their cards right they will have actually used Google to steal at least some of Google's search traffic away from them.

That said, I also don't believe Twitter's long game is search. I think they're trying to re-invent how we access information. Instead of searching for something, what if you could subscribe to a topic and just get information handed to you constantly?