Hello. They receive a segnoirage revenue because of the loans they lend to the financial intermediates in form of interest. When there is a totalitarian government, out of economic issues, they receive security snd loyalty (I think it's a kind of profit).
It can be printed just for reduce public debt, what increases the monetary base and usually finishes in high inflation. If you print money for other purposes and that leads to a higher inflation, public debt decrease their value. So it's easier to pay it from taxes.