There is currently an article (in German) in the Frankfurter Allgemeine called "The Demise of San Francisco" [0] in which the possible reasons for this are discussed. One reason given (which I cannot verify as I don't live there) is: people are fleeing the city because it has become a terrible place to live:
Quote from the article, Google translation:
> Jayson Hill recently stopped by his old apartment. He didn't feel sad that he hadn't lived in San Francisco since the end of August. Instead, he thought of all the things he won't miss: the dealers on every corner who go about their business so bluntly that passers-by can see money and drugs change hands. The syringes lying around everywhere. The human feces on the street and the unbearable smell of sewers. Hill once saw a corpse on the sidewalk who had obviously died of an overdose, a coroner had just come to the scene. Hill ran into drug addicts so often that he learned how to give Narcan, an antidote to heroin and other opiates.
> Hill was once threatened on the street and was increasingly afraid to leave his house in the dark. "It was starting to feel like a terrible nightmare," says Hill. During a farewell visit to his old apartment building, he heard that ten other former neighbors had given up their apartments.
> Nevertheless, some companies are now adjusting to the fact that they will need less space in San Francisco in the future than expected. Pinterest has accepted a contract penalty of almost 90 million dollars to get out of a rental agreement in a new office building. Twitter has just offered part of its headquarters to sublet. CEO Jack Dorsey has already said before that he no longer wants to be as focused as he has been in San Francisco. Other companies are also loosening their ties to the city. When the software company Oracle announced that it was relocating its annual mega-conference "Open World" to Las Vegas, the reason for this was not very flattering: It was not only the costs that were decisive for this decision, but also the desperate conditions on the streets of San Francisco.
[0] https://www.faz.net/aktuell/wirtschaft/obdachlose-und-drogen...