There have been many failed and successful assassinations of political leaders or other public people. You think if John Lennon had survived his assassination he should have taken it as a wake-up call and revisit his values and public stances?
There is many good reasons why Trump should start introspecting. And if he would develop some sort of empathy and decency probably the pain of seeing who he was and is would kill him better than any bullet could.
But this is because he is Trump. This is not because someone wanted to kill him. All sorts of people want to kill all sorts of people for all sorts of reason.