Everything we know about the biology, chemistry, physics and astrophysics makes alien contact with the earth an extreme improbablity. Everything we know about government and intelligence agencies makes a global, mutli-national, multi-government, mass conspiracy to hide aliens an extreme improbability.

Against these mountainous-weights of incredibility one needs more than a retired 36 with a shiny badge who has "heard but not seen" some things.

The improbability of his claims is so vast that even "CIA psyop" becomes plausible against them -- not, least, since it's extremely likely the USA exploited the UFO mass hysteria to disguise its air force development programmes.

Nevertheless, the most probable explanation is that government employees in these agencies are often paranoid believers in the folk mythologies of these agencies --- and are able to maintain these superstitons because they never get senior enough to see they are false.