The United States has such a large GDP because 1/3 of it is the private healthcare industry. Another massive chunk is the government throwing tax dollars at a shell company of a shell company of a shell company that moves a government contract for construction around to each other 4 times, all subsequently increasing GDP.
This is exactly how the MIC works. Wildly high bids/price fixing for the Pentagon, and the brass own stakes or even outright own the companies that fleece the government.
If they don't directly own shares, they've got a sweetheart gig on the company's board lined up for when they 'retire'.