+1 The crash was 100% caused by the extremely stupid and reckless policeman stepping out in front of the motorcycles.
You could argue this back and forwards all day long. There wouldn’t be any opportunity for an accident if no one had been riding a motorbike. Of course, just the act of riding it doesn’t put you at fault. But because it’s an inherently dangerous activity, and you’re not only responsible for your own safety but that of others too, there are rules and guidance to adhere to. The ones that come to mind here are, the speed limit, maintaining an appropriate stopping distance from the vehicle in front, and adjusting speed to the conditions of the road.
I’m fairly certain the accident would not have happened if the rider hadn’t neglected all of the above.
Those rules are there because unexpected stuff does happen. And when it does you should be in a position to react to it. That’s your responsibility to ensure you can do that.