My memory of a quarter century ago isn't nearly as rose coloured. I remember a nation hell bent on revenge. People with even a hint of middle eastern descent were viewed as terrorists. A Sikh (not even the same region) was beaten because of his headwear. The country was just as divided then as we are now.
200 yds isn't the most difficult shot with a zeroed in rifle and a practiced shooter. Beyond that, the who and why is purely conjecture. Maybe politically motivated or maybe some dude trying to impress an actress like Hinkley did.
Charlie Kirk was a divisive horse's ass. He said "Your body, my choice" Ya'll pick some strange heroes. Doesn't mean he deserved to die. But he wasn't a good person.