Sure, you can create a lot of economic activity by building a lot of stuff and blowing it up, but in the end all you get is still a bunch of rubble. Pouring most of your economy into building rubble generally doesn't end well.
If it is rubble in other countries and you get to extract the ressources from under it, it might work out unfortunately.
Given how we still go full steam ahead into the climate catastrophe, wars will be back on the day to day schedule also in Europe. And each country has their own version of the MIC making big big bank with it, while the world burns.
Heck if you look at Germany, some of the worst nazi supporting companies became global conglomerates and the families behind them are more obscenely rich than ever before. So even turning your own country into rubble is a perfectly working strategy under capitalism.
I have seen analysis of this on modern wars and essentially none in the 19th or 20th centuries have produced positive ROI's. It worked when power was so asymetrical that the great powers could easily conquer giant territories, but those days are long gone, as we can see in Ukraine.
Positive ROI for the country or for individual actors in the country? Because talking utility, wealth or wellbeing on a state level there is a lot of things, done terribly uneconomically. But the obscene wealth of the few is the detriment of the many.