Do bears even have the reasoning skills to do this? Every bear I've met has just been like "Food!" or "Maul!"
They've never been like, "Son, I can't stand thinking that you'll live a life of torture. We're both going to go to sleep now. Close your eyes and don't open them. Mommy will see you when you wake up."
What animal can't tell when it's distressed?
Enough to mercy kill it? Or even realize what a mercy kill is?
What animal doesn't know what death is?
Mercy killing is something many humans would struggle with. You're telling me a bear has the complex brain power needed to understand that and then make that choice?
Is it more likely that we're just assigning human like reasoning to an animal? Could the bear simply just have freaked out due to torture instead of weighing the complex intricacies of it's child living in pain.
This is a bear. An animal notorious for doing anything it can to keep it's cubs alive. It has very strong instincts to not do this and they're not geniuses of the animal world. It more likely just went mad from torture imo.