But some grizzly/brown bears still stalk and kill and eat humans.
There are several documented cases.
Hunting is opportunistic, generally.
The vast majority of bears, of all species do not hunt humans. Polar bears, generally do not hunt humans because they are uncertain of humans as prey. They are very dangerous, because they may not be afraid of humans, and can easily decide humans are worth predating on.
The motivation of grizzly bears which kill humans in surprise attacks or of sows with cubs, is not obvious or certain.
Hererro gave his opinion of what he thinks the bears are thinking, but it is just his opinion. The only reason he makes the claim the surprise and sow with cubs attacks are not predatory is because they do not usually eat the human immediately. Leave the body there for a few days, and the bears tend to eat the humans.
Bears are surplus killers. They will kill things, just to kill things. If they are not hungry now, they are likely to come back later to feed.
I tried to find it but Jim Fowler of Mutual of Omaha Wild Kingdom fame had a list of animals that preyed on humans. I remember him mentioning polar bears and crocodiles but there were more.