Earlier quoted context omitted.
Why do people sit on empty homes then, in the face of rising supply of luxury homes? The demand side of the equation is unable to finance a purchase. The wealthy can wait until they get the gains they want. There's nothing circular about it.
They're sitting on empty homes because there's not enough supply. Without solving the supply issue the wealthy will keep using residential real estate for investment purposes. The wealthy aren't waiting around to buy/sell houses per se, they're trying to get a maximum return on investment. Adding enough supply so that housing isn't an investment vehicle removes those incentives.
Who will add luxury apartments or affordable apartments except for the already wealthy? Who has the incentive to build enough luxury apartments, to stop housing behaving as an investment vehicle?