GDP was developed in the US and is particularly slanted towards war economies. That "home field advantage" makes a huge difference.

Example math not from actual statistics but to make a point.

If 10 US MIC related companies each make $500 bn, together that is $5 trillion, or one quarter of the US economy. Each company will have on average 100k workers, in sum 1 million. That is a tiny proportion of the US work force.

The real issue is that war products have zero domestic leverage. The Raytheon worker's pay is accelerated through the economy, but a Raytheon missile does not do anything to improve the efficiency of other US businesses.

I don't like Elon Musk, but an efficient US electric semi-truck would actually make US deliveries more efficient and thus help the US economy grow, not just for the truck manufacturer.

You get the picture.