Earlier quoted context omitted.
This argument doesn't work when the Federal Reserve, an entity unconcerned about ROI, is purchasing bonds out of thin air. They now own $7 TRILLION of US govt bonds. This number was less than $100 billion before the GFC. https://www.pgpf.org/blog/2021/01/the-federal-reserve-holds-... So, yes, no investor wants bonds. Why would you buy something that's a guaranteed loss? It's increasingly just the Fed.
What happens to a bond when the Fed buys treasuries? Are they "cancelled"? Or does the Fed actually hold those bonds? The latter sounds nonsensical, but I don't know enough about how the Fed works.
There is a predetermined amount of the Fed dividends which gets payed to the constituent banks, and the rest is given back to the treasury.
The same happens for the European Central Bank, and AFAICT, most central banks.