Misfits are everywhere
By 
Thomas Crooks looks likely to end up falling squarely into the “misfit/loser with no coherent political ideology or goal who attempts to kill the president on a whim, out of a grandiose desire to be somebody” category of would-be presidential (current or former/very possibly future) assassins.
This category fits Lee Harvey Oswald and John Hinckley very well: Hinckley tried to kill Reagan because he was trying to impress the actor Jodie Foster, who played an underage prostitute in the film Taxi Driver, which Hinckley watched dozens of times.
Oswald was a Marine who defected to the Soviet Union, which was a minor news story at the time, became disillusioned rather quickly, and was frustrated and enraged when his return to the U.S. was ignored by the media. A few months before assassinating Kennedy he tried to assassinate Edwin Walker, a far-right wing general. Oswald seems to have had vaguely leftist but basically confused political beliefs, but his assassination of Kennedy was a purely opportunistic and impulsive crime: he read in the Dallas paper on either Tuesday November 19 or more likely Wednesday the 20th (he was too poor and cheap to actually buy the paper and usually read day old copies in the break room of the Texas School Book Depository the next day) that Kennedy’s parade route was going right under his window. The parade route had been selected by the Secret Service on Sunday, and wasn’t publicly known until Tuesday. Oswald decided right then and there to shoot Kennedy, because he was an extremely impulsive extremely violent nut. He almost beat his wife to death on several occasions, a fact which is wildly understated in the Warren Commission report, and he seems to have shot Kennedy pretty much completely on a whim, because he wanted to see his face in the newspaper again, after having been slightly famous for 15 minutes five years earlier.
The two women who tried to shoot Gerald Ford don’t quite fit this paradigm. Both were also social misfits, however. Squeaky Fromme was a crazed cultist, who literally worshiped Charles Manson (according to Vincent Bugliosi Fromme and Sandra Good were the only members of the Family who never renounced Manson), whose inept assassination attempt — she had four bullets in her handgun but had (inadvertently?) ejected the one in the chamber on the kitchen floor before heading off to try to shoot Ford — was a product of her unhinged worship for Charlie rather than a desire for individual fame.
Sarah Jane Moore comes closest to having something like an actual political motive/goal in shooting the president, but she doesn’t really come very close. She was a 45-year-old with a deeply chaotic personal life — she was divorced five times — who suddenly got fascinated by the Patty Hearst case and the Symbionese Liberation Army in 1975, and decided to shoot Ford to spark a social revolution: a goal she attempted to accomplish with a .38 caliber revolver she had bought that morning, and didn’t really know how to shoot (she didn’t know how the sights worked on the gun, which is probably why the shot she got off from fairly close range missed Ford. What a country.)
Crooks seems to have been a lonely bullied high school student, with few friends and not much of a social life. He apparently acquired the AR weapon he used to try to shoot Trump from his father, whether with his father’s knowledge or not is yet to be determined. He doesn’t seem to have had any kind of social media profile to speak of. He gave $15 to ActBlue two weeks after Donald Trump’s attempted autogolpe, but then registered as a Republican the following September. If he had any kind of actual political motive for his act, I suspect it was very much as confused and grandiose as Oswald’s and Hinckley’s.
BTW the story of how this kid got off several shots with a high powered rifle at Trump is really wild. Several people saw him acting suspiciously and then climbing a ladder to the roof of a building 150 yards from the stage. The area in question was being (not) secured by local law enforcement rather than the Secret Service, and they pulled a Keystone Kops routine when bystanders told them there’s a weird guy trying to climb onto the roof of this building overlooking the rally stage. A local cop actually followed Crooks up the ladder, and confronted him on the roof. It sounds like the cop never actually got on the roof, but retreated when Crooks turned toward him with his weapon. Then Crooks got off a bunch of shots before Secret Service snipers killed him. The most amazing aspect of this story is the complete lack of communication between the local cops and the Secret Service, as the former spent several minutes frantically trying to find Crooks without the SS ever hearing that there’s a man with a gun over there.
The moral of all this is that we live in a country where unhinged loners, who are about as far away from being professional assassins as its possible to be, can still come close to or one case actually succeed in killing occupants, past and possibly future, of the Oval Office, despite the vast resources that are dedicated to trying to keep this from happening. This might possibly have something to do with the 300 million or so guns/firearms/weapons (apologies to the ammosexuals for getting the terminology wrong in some way probably) floating around, along with enormous amounts of social alienation, a culture obsessed with fame and unable to distinguish it from notoriety, and lots of untreated mental illness, Undercooked political ideology marinating in the fever swamps of the Internet is now also no doubt playing a role, but again I suspect it was a secondary factor in this particular case, and in the cases to come, as things fall apart and the center does not hold.