There are complicated issues but there are also obvious ones. Fewer people downtown- fewer office workers due to work from home, fewer conventions due to COVID fallout, fewer tourists. Perhaps more people buying online. Perhaps people spending less money on non-essential goods due to inflation. These obvious issues are caused by various factors some of which are out of the control of the City and some of which are arguably in the control of the City. So less traffic for retailers; stores will close.
The BART rider figures also tell the story.
I believe the city has fueled the situation and made it worse by not reacting to business concerns. At the point when the businesses complain it may already be too late but this city didn't even try to address the business concerns until a lot of them started closing. Nordstrom seemed to be the biggest wake up call for the city leadership. However that is not the whole problem here. The city could go into hardball mode tomorrow and put police in front of every store and it wouldn't make these stores stop closing. There are a lot of factors. And it may be there just won't be enough people in the area anymore to support these stores no matter if the crime is all stopped tomorrow.
The fact that historically San Francisco has been one of the highest cost places to do business (rent, wages, etc.)... so these retailers automatically need to do more volume there than a typical store just to cover the increased costs. Historically that was not an issue but with the loss of office workers/tourists...
And those high costs were created by groups who priced everything artificially high and pushed people who were barely getting by out too. Or groups who took older buildings that housed individuals/businesses at lower rents due to building age/building being fully paid off/building with low property tax due to old long term ownership, and borrowed a bunch of money then "redeveloped" them into "luxury" buildings priced not only to factor in the debt payments on the money they borrowed and their redevelopment costs but also their desire for maximum profit on the rentals.
You know how retail goes. If you lose 15-20% of your sales your store may be doomed. Anywhere it is located.