Very true but a failed impeachment causes less disruption than a successful assassination.
Actually, Assassinations are kind of useless for changing policy.
Killing JFK didn't change anything. LBJ continued with the same policies, and was probably more successful in implementing them.
Killing McKinley didn't change anything. Teddy Roosevelt continued on with imperialist policies by the US.
Killing Garfield didn't change anything, as he and Chet Arthur were inconsequential presidents.
the only argument you could made for an assassination being disruptive is killing Lincoln, because Andrew Johnson was so awful as a President. But it is unlikely that if Lincoln had lived that Reconstruction would have been less of a clusterfuck.