Governments are one of the few entities that are able (and occasionally willing) to spin up a mass production endeavor without the profit motive necessarily present.

Sometimes they essentially do this themselves via federal employees, or contractors. Sometimes they achieve the ends indirectly by incentivizing private companies with subsidies and the like.

Regardless of how it gets done, everyone shows up for work in the morning motivated by something. In the Soviet Union this was often the fear of imprisonment or other such violence, which was a really shitty situation for a lot of people to be in. In the modern world, it’s typically the hope that the money made will pay for food and housing and such.