A 1999 Secret Service study on political assassins gives us a glimpse into the minds of some very disturbed people. NPR summarizes:
Perhaps the most interesting finding is that according to Fein and Vossekuil, assassinations of political figures were almost never for political reasons.
“It was very, very rare for the primary motive to be political, though there were a number of attackers who appeared to clothe their motives with some political rhetoric,” Fein says.
What emerges from the study is that rather than being politically motivated, many of the assassins and would-be assassins simply felt invisible. In the year before their attacks, most struggled with acute reversals and disappointment in their lives, which, the paper argues, was the true motive. They didn’t want to see themselves as nonentities.
Even Oswald, who is seen by the casual observer to have murdered Kennedy because the assassin was a Marxist, fits this profile far better than the superficial view that politics was involved (although Oswald used his supposed loathing of capitalism as a justification).
The profiles of assassins that emerges is far more like a John Hinckley, Arthur Bremer, James Earl Ray, or John David Chapman than a Booth who was part of the only genuine (known) conspiracy among political assassins in America. It appears that the desperation of their own lives was far more relative to the cause of their behavior than any political views or political movement.