Approx. 30 years ago I worked in downtown S.F., and frankly the seeds of the “doom loop” go back a lot further than many realize. In a lot of ways, this has been a long-term decline that was largely “papered over” by a tech/startup boom that have supplied a steady stream of boom/bust office tenants for the past 25 years.
Allow me to explain... ~30 years ago, downtown S.F. was the headquarters of a half-dozen or so really big, traditional companies that each employed thousands to tens of thousands of workers: Chevron (aka Standard Oil), Wells Fargo, Bank of America, Pacific Telephone, Pacific Gas & Electric, Charles Schwab. Bechtel. Through various mergers and moves, every single one of those companies’ headquarters eventually moved out of S.F., with maybe 80-90% of their erstwhile workforce gone. Yes, the Twitters and Ubers and Airbnbs came in and hundreds of lesser imitators rolled in, but it wasn’t the same thing. The tech companies and their workers come and go. It’s a totally different thing than the Chevrons and Wells Fargos that had the same boatloads of people working there for 20 or 30 years. We can talk about the crime and the drugs and all that stuff has hurt, but the fact is that SF cast its lot with a startup-tech industry that has proven unreliable over the long term.
Your observation is true for dozens of cities across the USA. Our politicians and business leaders sold out the country.