John: Central basks have been around for a long, long time.
This is anecdotal, but prior to 2008, western countries were selling bonds to emerging economies like Russia and China to finance western government deficits.
And of course, factoring allows government to turn a $1,000,000 bond from the Russians into 10x that amount to finance government operations.
After 2008, this source of bond buyers dried up. Western governments had to invent other buyers to keep the government deficits going. And that is that third central bank where the government is both lender and borrower. Basically, the money supply is increasing. This may be manageable in normal times, but one wonders about the consequences with Covid-19 shuttnig down some of he economy.
I found monetarist economics confusing before 2008. Now it is more confusing.