Simply put it's tied to opex + cost of capital. And is opportunity costed against other investments -- but keep in mind real estate has high exit costs (realtor). So you'd have to think you can do much better on another investment to sell (and drive the asset price down) for it to make any sense.
The insight is that the cost of capital is roughly fixed at the time of purchase. If someone bought a place in 1970 they can price bid down to nearly nothing because that's their operating cost and the purchase price is only a fraction of landlords who bought recently.
Supply and demand create the conditions where landlords either compete on price, choose to sell, or potentially declare bankruptcy.
Asset pricing is what's correlated to rental affordability. If the tenant class, in general, can't afford rent increases, rent won't increase, and real estate asset prices will stop growing, all other things being equal. Obviously, if money becomes cheaper for landlords, then they will borrow more of it to buy the same properties. But this does not give them any more power to unilaterally set rents.
But all in all, the tail does not wag this dog.
It's not, though.
In a very simplified toy model, maybe there should be a direct 1:1 link, but empirically in reality there isn't even close.
Rental affordability is 100% correlated to asset pricing.