In particular, the central bank, charged with controlling inflation, cannot use taxation to reduce the money supply, because banks do not get to set tax policy. That leaves raising interest rates as its only policy tool.

As the political arm of the government chooses to run deficits in excess of growth plus inflation, then (a) that causes more inflation, and (b) the central bank raises rates, increasing the cost of government borrowing, causing bigger deficits.

This escalates as a result of the central bank trying to control the effects of high government spending by applying a mis-matched policy tool (interest rates) in place of the politicians who have abdicated their responsibility to use a matched policy tool (taxation). Either it spirals out of control, or more and more of the government budget is devoted to interest expense (direct government transfers of wealth paid exclusively to the debt holders) and less of it is spent on providing actual government services (that benefit all taxpayers).

If the central bank does not raise rates, of course, things go even more badly.