I can only think of two explanations:
1) The usual knee-jerk decision to "protect" the American people by hiding the truth from them. They don't want a panic. They don't want anti-Arab sentiment to grow. Heavens forbid that people might grow suspicious of Muslims. They don't trust the American people to defend themselves. Probably this is part of the answer; but there is also a second reason, IMHO.
2) The well-known fact, never admitted by the MSM, that Oklahoma is crawling with Muslim extremists (partly because Arabs are sent to the University of Oklahoma for oil field training), and these people include large number of Saddam's Republican Guard, sent over here after the first Gulf War, and large numbers of terrorists who were double, or more accurately triple, agents working for the FBI.
These people were up to their necks in the OKC bombing, as were the FBI and the CIA, possibly on clinton's orders. In other words, the FBI is full of people who were corrupted by clinton, have close connections with Muslim terrorists, and can't afford to open the doors and let the daylight in. Regretably, Mueller has done nothing to clean these people out of the agency, but has actually promoted them and given them medals.
Just as there is a rogue CIA contingent, so there is a rogue FBI contingent. And so far the President has done nothing to grapple with the rogue FBI contingent.
Thank you. I think you're exactly right. I know there's reasons to "protect" the American people, but I think when you balance them against the reasons to reveal what really happened and who did it, the government would be much better served by honesty.
Reason number 3 is simple and financial. Huge money involved in sporting events live and in person, not to mention the monetary endowments Universities receive for the teams. Scare people away from that (and pro games) and some big dollar folks are going to come up waaay short in the till.