Well Teslas are known for their incredible acceleration, and then if the occupants weren’t wearing seatbelts, even a relatively low speed crash can cause severe injury.
Tesla autopilot doesn't exploit that, though. The question is how they launched the car, and how they managed to launch it into a tree. You just can't do that with autopilot to my eyes.
How fast would they need to be going for this to be fatal? I could definitely see autopilot missing this turn and crashing into the tree, and it’s possible they were trapped inside rather than killed on impact.
The whole front corner wrapped around the tree. That's a highway-style crash, so figure 50+ mph I'm guessing? I have a hard time imagining the front passenger survived the impact given the way the cockpit collapsed, but maybe the back passenger was trapped.
