They know that their large economy will deteriorate once they engaged in a war. They cannot afford to go back to the old times when they've got no infrastructure yet.
Politicians live in bubbles, they won't notice if their country ends in Caos.
They don't have to notice it because they've got some properties and have got dual citizenship on a much safer country.
No country needs conflicts still many live to be in one. The war in Ukraine does not benefit Russia, still that won't stop Putin.
It doesn't benefit both parties if we're talking about the citizens and even us that are far from there. It only benefits the ones that are at the top of it.