but there could be so many reasons why...

Exactly. My family and I went through the sadness of watching one of our pet cats wasting away to starvation a couple of months ago, despite the abundance of food that was available to him. He would meow for food all the time, but then just lick the surface without swallowing when you gave it to him. It turned out that he had intestinal cancer that was preventing him from eating. He only survived for his last month or so because the vet prescribed prednisone and my wife and I were loading him up with fluids under the skin and force-feeding him with baby-food and pureed cat food in syringes three times a day. In the end, even that care wasn't enough. He couldn't even stand under his own power and looked just about as emaciated as that bear when we took him to the vet for his last visit.

Just yesterday, we had to put down a nine year old German Shepherd Dog because of a degenerative condition that prevented her from moving around very much (probably hip dysplasia). She developed compression sores, and those got infected. If she had been a wild animal, she would have been unsuccessful at hunting and starved to death months or years ago.

It is heart breaking to see, but animals have been getting sick or injured and starving to death since long before climate change became a concern. If I had to guess, I'd bet that the bear was far more likely to be starving as a result of a more traditional illness or injury than from climate change.