Perhaps foreign governments have suspicions, and whatever agency sent it up wants them to think that it failed.
Otherwise, there was a failure on the Northrop Grumman side of the house (they were responsible for mating the payload to the second stage adaptor at their facility due to the classified nature) or this was an ICBM reentry vehicle demonstrator.
If you listen during the launch stream, you can hear where video telemetry control is relinquished and passed off to secure ops. That telemetry should make it obvious if fault needs to be assigned.
It is not yet certain this is not a misinformation campaign (which would not be without precedent [1]).