This was a human driver, Tesla's don't have a real autopilot system that can literally drive the car for you. The "autopilot" feature is just to avoid collision

This was a human driver, Tesla's don't have a real autopilot system that can literally drive the car for you. The "autopilot" feature is just to avoid collisions, so in this case it just applied the breaks when it detected the car moving in front of it. In addition, the right lane probably had so much traffic because it was an exit. In this case no one in that lane is going to suddenly hop into the left lane (they would obviously miss their exit if they did). In that situation it's really not that ridiculous to be driving that fast.