I don't think it was theater. The US Navy calls the Canadian Navy up on the phone, and says, just for fun: "Hey, you guys still run P-3's, right? We got rid of them, as you know, and these new things just don't work as well. Could you give us a hand?"* We did a real search because nobody was positive enough to walk away from it, with a chance that they could have been alive, on the basis of a 'bang' noise. If they'd released the info sooner, there would be a continuous argument over whether or not the search was pointless.
The only reason to release the info would be to save the cost of the search, if they were 100% certain it imploded. That's a big risk. Who wants to be the one that makes that call, then 20 years later we find out they were really alive at the bottom, writing notes to their loved ones until they ran out of air. See the Kursk disaster for an example of that...that was horrible.
So we did a gigantic search for 4 days? No one hurt, everyone gets a bunch of practice working together, great training exercise. And maybe a better reminder to people that homemade submersibles may be a bad idea.
*I may work with a guy who was former P-3 crew.