It IS more complicated than that. It's not easy to build within a 1 hour commute of a dense population center. All that land is owned, built, and called for. Calling it "overpopulation" could be fair.
A parallel problem is immigration and, as the top comment pointed out, cheap credit encouraging vacancy.
No one wants to say it, but immigration is a huge driver of housing un-affordability. Skilled H1b immigration and/or foreign buyers drives up home prices, and unskilled illegal immigration drives up rents.
A parallel problem is immigration and, as the top comment pointed out, cheap credit encouraging vacancy.