The ultimate reason the wealthy are earning so much in rent is housing supply shortages.

It’s actually a trend since 1980s. Things like deindustrialization and financialization, outsourcing (which collapsed the unions), deregulation (incentivizing externalities primarily felt by the working class - the 2008 collapse, environmental deregulation in Louisiana, etc), inflation (which benefits those with assets and harms those without), tax cuts for the wealthy. The wealth gap grows which means assets like housing shift to asset holders (the wealthy). This in turn allows asset holders to increase cashflows from the working class to the ownership class in a feedback loop.