Hersh writes:

The C4 attached to the pipelines would be triggered by a sonar buoy dropped by a plane on short notice

Baxter wrote:

One of the P-8’s sonar operators, however, gave JAG investigators an entirely different story. He wrote in a sworn deposition that the P-8 dropped the first buoy directly over where the explosion had taken place.

It seems the sonar man was not in on it, and the pilots were sworn to secrecy by some admiral loyal to Biden. The sonarman is unaware that his buoy triggered the explosion. The aircraft's flight recording data is missing, because it would reveal the buoy was dropped before the explosion, not after.