Sure, people were wrong in their assumption that the murder was random. At least that's how it looks now. We haven't heard the suspects side, but....
But wrong that SF has become a dangerous and mismanaged city? Murder isn't the only violent crime and a lot of crime goes unreported. People don't feel safe walking around and you can't just dismiss that. It's their "lived experience". The fact that everyone assumed that Bob Lee was murdered randomly says something about the state of the city.
SF has a lot of issues and it has a lot of crime and other issues. It has been mismanaged for years now and things need to change.