more prosperity in peace, more money in peace, but more concentrated profits in war

I genuinely don’t get war at this point. Do people waging these wars think that they are going to just be able to control the territory afterwards? Like it’s nothing? Why destroy all of the infrastructure of the place first? It truly just seems like they enjoy destruction. How many years will it take to recover your own economy and quality of life afterwards?

How does any math work out for anyone who isn’t rich? How do militaries go along with it?