They say the dog played dead to avoid being killed. I am not so sure. I prefer the theory that the dog was passive because of fear and the realisation that he/she could do nothing. It was game over for this dog until the lioness was distracted by another dog and let go. I am surprised the lioness was distracted. Wasn’t that carelessness on her part? Perhaps the other dogs made a conscious attempt to harass and fluster the lioness in order to save the life of their group member. The African wild dog (aka ‘painted hunting dog’) works in organised packs. They work together and I’d expect the others to try and save their colleague.
Two useful tags. Click either to see the articles: Speciesism - 'them and us' | Cruelty - always shameful