"The cause of the accident that led to the submarine sinking in just four minutes has never been established.Hmmm. They knew it took 4 minutes to sink, but didn't raise the alarm until the next day?
...
Initial reports suggested the submarine may have had rudder problems before sinking. It was engaged in an exercise with a military aircraft when it disappeared at about 7.55am. The alarm was raised when it failed to return to its base the following day."
The article mentions a seismic report suggesting an implosion. Perhaps that provides a time index that wasn't available until the first investigation began.