People fight in response to imagined outcomes. Even though what you say is the accurate picture of all warfare (wealthy interests ordering poor men to their deaths so that the wealthy can maintain their "interests"), people fight because their imagined alternative - which is being taken over by their enemies - is even scarier. For the history of humanity, soldiers have always fought in a permanent state of 'better the devil you know that that other devil'. For Ukrainians, the Russian devil is the current occupant of their nightmares. For Russians, the US/Davos devil is that occupant.

It takes a LOT of abuse from the current devil before that dynamic can be broken. It happens occasionally (1917 Russia, for example), but it's a remarkably consistent response. Human nature hasn't changed, just the technologies we use to slaughter each other.