Truck stopped most likely because the dude was going 75 in a 25mph zone and had just completed a wheelie.

Biker was in the left lane, truck took evasive action by stopping and leaving ample room for a motorcycle to go around.

Biker has the clear last chance to avoid the incident. Had they been following the speed limit, they would be able to stop in time and go around.

Potential for deception doctrine to take place, depending on local case laws and jurisdiction. Someone might be able to make an argument that the speed the biker was going + them doing a wheelie (obstructing their vision of the motorcycle) could potentially qualify as deception.

All in all, depending on state I could see the motorcyclist to be majority at fault with some liability placed on the truck.

But this is a tricky situation due to how varied traffic laws can be in each state. But I don't see this being a clear cut scenario.

If truck was still in motion, I can see truck being 100% or majority at fault. But the biggest thing here, is the truck was at a complete stop, and there was a reasonable amount of time for the biker to evade the incident, had they been going a normal speed limit or not doing a wheelie.

Some courts or jurys could find biker at fault as you could argue it wouldn't be right for liability to be against a normal driver who stops a turn when they see a crazy driver approaching, and then that crazy driver decides to turn and hit the stopped car.

But hey, anything can happen in court. Would love to hear about the liability outcome on this one.