The fact is, the housing crisis is and always was a policy failure and a "distributional outcomes" issue, and and no amount of improving housing construction's speed, costs, or legality will fix it if we don't both change policy and reduce inequality
There are tons of building that are or could be residential housing that are owned by massive investment firms as a speculative asset. The FTC's recently published brief mentioned that keeping units empty rather than lowering prices is common practice among landlords. Even among individuals, an incredible amount of older, wealthy people own multiple homes and view most of them as a source of passive income. When I talk to people in that category, if they are doing well, they are often thinking about buying more homes to generate more income directly from renters or as a speculative investment (IE to hold and sell later)
As it stands, people are not homeless because there is nowhere they could live. Not even close. Increasing housing supply without making any significant dent in the financial and regulatory situation surrounding housing will more likely just put more real estate in the hands of the entrenched winners, who have already demonstrated the willingness and ability to hoard housing