The government hides everything that does not fit the narrative that keeps them in power.
One of the greatest things that could ever happen to this country is if a law was passed that stipulated that the government had exactly 3 months to reclassify exactly just 1/4 of all currently classified documents and that the remainder would be dumped onto online archives for any to see.
I used to make stuff under defense contract for the US military. Every design spec and everything else that was associated with the project was highly classified and we had the security measures in place as instructed. Thing was we made exactly the same thing that was sold on the open market using the same production lines. Military paid 300% more than our distributors.