It has nothing to do with the technology sector directly; It's just about money and the pendulum swinging back towards urban living being considered desirable. A booming sector of the economy combined with a relatively affluent portion of the population wanting to move into geographically constrained areas that have been neglected in terms of development for the past few decades.
And a large number of now rich people in other countries looking for assets outside of their home country's control - which in SF is just the same as it is in London