The campground, where this took place, is on the edge of a small town (and close to a second small town. Grizzly and black bear are routinely sited in people's backyards in this area. A photographer that I have met, that lives in this area, had a moose calf taken down in his front yard, by a grizzly. Highway 212 goes through this area and town, it's a human populated area with much wildlife. It's an area where there are people living there, many people passing through the area on their way into the NE entrance to Yellowstone, many people recreating in the campgrounds, people using the myriad of hiking trails, people fishing in the streams, people using their ATV's on the trails in the Gallatin National Forest, where this happened, people vacationing in owned or rented cabins, people use this area as a base to backpack into the surrounding wilderness.
This particular area is a beautiful place, a wild place, but not a preserve or an untouched place. Bears that pass through or live in this area, know that humans are all around, and vice versa.
Having just recently been in Cooke City, the town where this tragedy happened on the outskirts, last week, for my seventh visit to that area, I can say it really doesn't make much sense to de-populate and remove a whole town, population and the businesses that have been there for the last century because of the wildlife that lives in the vicinity. The people that live there, do not live in fear, they are aware of their surroundings, take precautions to not make their places an attractive nuisance to the wildlife, practice smart behavior when hiking and recreating on the surrounding trails.
Having said all of that, my speculation on this grizzly sow and her 3 cubs and what caused this tragedy to happen, in my opinion is she was food habituated by humans. Somewhere along the line, maybe not in that instance or on that day, but at sometime this bear was fed by humans (Vacationers staying in a nearby cabin, or campers seeing this bear family on the outskirts of the campground or along a trail... and they wanted to keep seeing the cubs and the mom, so they threw a sandwich toward it or a candy bar... "Oh look, they are so cute... they are walking away, throw that sandwich toward it and see if it will stay a little longer!") or this bear and family had come across discarded food in a campground setting (I've witnessed this myself, idiots in bear country, vacating their camp and leaving discarded packages of junk food, leftover food thrown into the fire-pit, all possible attractions to any nearby wildlife, including bears) and finding that food, started to associate campgrounds/human populated areas with an easy meal. Bears are very opportunistic and once they find an easy meal, they will revisit an area hoping/expecting to find another easy meal. Once that bear has become habituated to come into areas where people are, of course the potential for problems and confrontations skyrockets.
Despite what the media portrays, bears in this area are not lurking behind bushes, waiting to pounce on any stray hiker or camper. Bears there, as just about anywhere, for the most part, want no business with humans. Just stay out of their personal space and leave them unmolested and they will go about their business of foraging and doing their thing and no harm happens. Bear attacks do happen, although they are very rare. Most are from approaching too closely, either by stalking one for a photograph or a closer look, or by accidentally surprising one by not making noise and making your presence known before you are too close, or encroaching on a bears food. The predatory attacks, like this one, are almost always from people either not keeping food or other attractants put away properly or the bear being habituated to humans and their food in prior instances.
A very sad thing that this man was killed. This really is a very rare thing to happen. If my speculations are correct about the causes, I'd really like to see much harsher and stiffer penalties put on anyone that does anything to habituate a wild bear. You intentionally feed a bear?... here, a $10,000 fine and mandatory 30 days in jail. Let that word get out a bit and I would think more people would think about their actions instead of being thoughtless and causing problems for the wildlife and possibly for other humans that might be in the area after them.