In the video the most sensitive areas of the child were missed. The tires ran over the child's arms and legs. That probabaly hurt, but I certainly wouldn't expect it to be fatal with proper medical care.
This looked more serious, but the child's head was also spared. The tires didn't linger on top the child for long, but I would be shocked if there weren't some internal injuries. Again, probably not fatal with medical care.Here is another video
A young child's bones are still growing and are somewhat flexible which would help. I'm a paramedic and I've seen kids (adults too) survive injuries that I was sure would kill them.Here is another video