There are many but the biggest is probably the destruction of unions, destruction of the social safety net (e.g. welfare et al), and especially the stagnation o

There are many but the biggest is probably the destruction of unions, destruction of the social safety net (e.g. welfare et al), and especially the stagnation of wages for nearly the last half century. If the minimum wage had kept pace with, say, per capita GDP since the 1960s it would be at around $20/hr by now, and if it had been increased gradually over time to keep parity with economic growth (as it had been for decades in the past) then there would be no great immediate economic shock to having the minimum wage "so high". And such a high minimum wage would also raise the wages of a lot of other folks as well, pushing up the bottom end of the wage scale, forcing a lot more of the economic growth since the '80s to have gone to workers instead of just corporate and millionaire profits/income. All of which would have led to a situation where it was much more difficult for climbing housing prices to force huge numbers of people into a homelessness that represented a huge uphill climb to get out of. On top of that there's the insane SF zoning problems and many other issues, but those are really just the icing on the cake, the core problem is the massive wealth/income inequality that exists in the US today.