One controller working tower duties, ground movement duties, coordinating with other ATC functions off the radio, an active emergency request, and giving clearance amendments all within 2 minutes. It's insane understaffing. On top of it, there was nobody there to take over after the crash. He worked the whole cleanup for the next 30 minutes.
This is an Olympian level elite Air Traffic Controller who was setup to fail.
I've visited towers, center facilities, and have flying (and some instructing) in the San Francisco airspace for 10 years. That kind of failure is systemic way above an individual.
It seems like less than 2 seconds from declaring intent to cross until they are told not to cross.
The runway entrance lights look red to me which is also a huge warning flag.