In the days after the Lincoln assassination the government actually investigated real conspiracies rather than ignoring the real ones while making up phony ones.
If our current “intelligence agencies” went back in time they would be trying to find John Wilkes Booth’s secret ties to the Czar.
Read anything written about psychology from 1963 - 1970, after the Kennedy assassination, and it is all about the violent sociopathic mind.
People tied themselves in knots for a decade trying to explain to themselves how somebody could shoot Kennedy, rather than just owning up to the fact that Oswald was a Communist, and Communists use violence for political purposes.
And McKinley and Kennedy were both assassinated, along with Robert Kennedy, several attempts on Ford and one attempt on Reagan that failed only because the bullet was badly made. Now that they’re not at all interested in who killed Seth Rich and why, and are hell bent to believe that the Russians did something Russian because Russian, things are looking bleak.