Democrats Must Fix the Housing Emergency (nymag.com)
Meanwhile, Real Estate was the top investment industry for Democrats in 2018 (for Rs it's #2). A big part of these investments are REITs (Real Estate Investment Trusts), which buy up rental properties in order to pay dividends to investors. More housing would negatively effect the value of these assets, so they won't help build any. It might be possible to make money building and operating new housing, but that involves work and risk. It's much easier just to make money on existing housing that will keep going up in value because of increased demand.
Top Sectors – 2018 – Personal FinancesPersonal Finances • OpenSecrets
A bit lower down the ladder (but still in an enviable position), we have the Democratic faithful like the boomer profiled in this article:
California’s Housing Crisis and the Fight Over 20 Townhomes – The New York Times (nytimes.com)
This is the widespread attitude of the backbone of the party, the upper-middle class suburbanites who provide the money, volunteers, and organization for the party. It's not just Nimbyism, they're are basically against more housing anywhere. If less kids sleeping on the street means lower property values for them, they'll have none of it.
Even looked at through the most neoliberal lens, this is total bullshit. The market could supply more housing, but the already well-off are making damn sure it doesn't happen so they can gain more wealth without any work. If this isn't justification for almost any form of resistance, I'm not sure what is.