Yes - Conspiracy Theory is a fact of Life, some of my experiences are founded in my work:
Military - I have first hand knowledge that our governments manages (tell lies) about info/material while was in the Navy during the cold war era. Sailors that figured out a likely scenario that was too close to the truth were hauled in and told to cease and desist or else, rumors that somehow got started were squashed, ships/subs coming in damaged got covered and the story was rough weather; and heaven help the one that got caught passing along info about our nuc - weapons. Then there are the Special Ops people - it just never happened.
AEC/DOE - go read some declassified material about our weapons production program and the impact on the environment. There are tons of reports sitting in govt libraries, but the catch is you have to have the background to understand what the detail is saying, and yes the magnitude of what was done to people and the environment is staggering.
If - Then:
For me, if the above is true, then what other programs drivers might validate the Conspiracy Theory? As has been said above, look for the motive (money, political pressure) for a coverup then assume it is a better than even chance that our agencies paid to protect us, will suppress and even lie about the evidence in question. For example here in WA we have the endangered species (e.g., spotted owl and native fish) situations:
Spotted Owl - just about bankrupted our timber industry here in WA/OR, based on the "fact" that the little owls would disappear if the old-growth timber went away. I had 600 trees on my land in Vancouver, WA and had a family of spotted owls happily nesting in my 22 foot trees. One can read forever about the fish on our Columbia River, and how the native salmon are endangered. Billions and billions are spent every year on this subject, and the theories about Cause and Effect are endless.
More and more I see these and many-many other issues get managed every year to the benefit of the few. So do government coverups occur - you bet by design, just in time and post-discovery. That is my reality....I wish I could still had the innocent, less complicated view of my youth.