Taken in order:
Video #1 -- Obviously, the car is at least 90% at fault here. There are, however, measures a rider can take to prevent this sort of accident. The assumption that a green light is a solid barrier to cross traffic, or that drivers always pay attention is a great way to end up in an E.R., or a morgue. If the rider had done a head check of cross traffic he would have seen the car approaching too fast to stop and taken countermeasures that would have prevented the accident. The point is fault is irrelevant if you are severely injured or dead. It's up to us to protect our lives.
Video #2 -- The fault in this case is about 90% the rider's. It looks, at least to me, as if the rider is doing a stoppie in the middle of a blind corner. At least the rear wheel was in the air and climbed up the grille rather than being submarined by the bumper, increasing the possibility of the rider being run over. As to the car driving away, the video doesn't run long enough to see what exactly the driver did, but it's possible either he was looking for a safe place to pull over or was afraid of the sheer number of belligerent "bikers" focusing on him. Either way it doesn't mitigate the stunter's culpability in the accident.
When I say "at fault", I don't mean the legal determination of blame -- rather the possibility of avoiding the accident.
I have lost two friends and one co worker to accidents and literally came within two inches of dying myself, and all
of those accidents were preventable given proper attentiveness and riding ability.
Be careful out there!