It's crazy to run into a burning building to save a child when someone else might do it. It's crazy to donate a kidney to your sister when a donation might become available from some unfortunate brain dead person. It's crazy for men to volunteer to die on foreign soil to defend their country when they have the means to fake a medical exemption. The only thing necessary for the triumph of evil is for good men to do nothing.
This is one huge false equivalency. All of these are immediate and recognizable emergencies, most of which would affect you directly.
The burning building is right in your face, and you can hear the screams of the children. Self-sacrifice and bravery is reckless, but not insane.
The kidney, it's your sister, you can see her decline, there's family pressure, and you'd miss her if she died. Again, self-sacrifice, much less reckless than the burning building, not insane.
The war, there's video of it, and depending on the situation, you may believe that the outcome may effective your own livelihood and freedom, as well as all of your compatriot, for generations to come. Self-sacrificing, high recklessness, but not insane.
Nobody asked Luigi Mangione to kill this guy. There was no family pressure, no publicly displayed motivating factors for him to do it. There were no videos of dying civilians urging him forward. He just decided to do it on his own, with no external factors urging him to do it. He knew it was illegal, if not wrong, and tried to cover his tracks, although he failed. Reckless, not intentionally self-sacrificing, not an obvious, direct emergency, no external motivation factor other than his own will, so yeah, nutty.
As for the "only thing necessary for evil to triumph is for good men to do nothing" platitude you put in there at the end, well, you go first buddy. You go first. Imho "evil" is just as subjective as "justice" a lot of the time. I don't appoint myself the arbiter of good and evil, that's for God to do. Beware of your own hubris, it will lead you astray.
