Everyone claiming that the autopilot is at fault for stopping suddenly get something very important very wrong: Stopping a car must be possible at all times. Any automation in a car should always be able to stop the car as the safe default. The same holds for human drivers, of course: Consider the possibility that the vehicle in front of the Tesla just lost some of its load. Of course the Tesla then has to stop suddenly. Considering this behaviour a safety problem is a lazy excuse. At worst, it is a nuisance.

As for the safety distance: This is a valid point. If the Tesla has not kept a safe distance to the following car when changing lanes, there is a problem with the automation. It should always be as defensive as possible. I don't see that from the police report, but the video shows the distance to be rather short, maybe two car lengths. Call it 10m. The second car doesn't really seem to brake very hard (no emergency braking assistant?) and that crash is definitely on the Tesla as it cut the distance, unless the speed limit in that tunnel would be around 20kph or so. But now it gets interesting: The third car does stop successfully. The big pileup happens afterwards.

In conclusion: The big pileup happens because the third car suddenly stops - and rightfully so but the following cars don't keep their distance to that third car. The Tesla getting rear ended is just a lazy excuse for these drivers that simply drive recklessly.