Do you think killing for example Hitler would’ve changed anything? He just was some random guy who joined an already existing movement (and even without that movement ww2 was inevitable after the peace treaties of Versailles and Saint-Germain). They’d just have picked someone else to lead it
Do you think killing Putin would change anything? He put complete loyalists everywhere, if he’s gone his political line will continue.
These are systematical issues, you can’t fix them as long as a large majority of those who have power to change anything (in a democracy thankfully that’s everyone who’s eligible for voting) simply accept it.
Side note: In the USA’s recent election ~32% voted for the Republicans and ~32% for the Democrats while over a third just didn’t care at all. That’s not how you get something to change in a democracy!
Faith in humanity restored