Earlier quoted context omitted.
The number of houses isn't fixed, nor are almost any other resource. The way economics works, each average person produces significantly more than they consume. Someone living alone in a cabin is (economically) poor. Someone in a small town may have customers, but not many, and it's going to be hard to expand. What you need is more people - more people buying, more people to work for you.
Housing supply is inelastic, in part because of zoning (but it's not the only reason). Know what doesn't change very quickly? Policy and law at the municipal level. Know what changes quickly because it's done at the very top level? Immigration rate.
Nobody is willing to go “long” on housing when the government can go “short” on supply at any time.
So you have to normalize that somehow, and since the government controls immigration levels, it should subsidize housing construction to match, somehow.