First, in San Francisco, to qualify for "affordable housing", you have to make under the poverty line in San Francisco. That means under 110k for a family of 4. If a builder were to want to build affordable housing to help these populations, it is not financially feasible without the government paying for it b/c one would have to sell or rent this newly built housing at significantly below what they paid for it.
So then enter rich white elitists like Preston and Peskin (with ties to the real estate lobby / land owners themselves) who want to enrich themselves by increasing the value of their own land. What do they do? They block all new housing development in San Francisco so the supply is permanently depressed and gate it on building "affordable housing". They package that up as a news story in helping vulnerable communities by making a few affordable homes but in in reality, housing gets more expensive and unaffordable for everyone.
Just so a few richly compensated officials can enrich themselves even more, at the expense of the poorest residents.