The article covers a lot of ground and differing opinions on why this is happening. There's talk of needing better education in the park (some attacks were the result of hikers not following clear rules) and dealing with the unprecedented loss of whitebark pine trees (a major food source for bears). There's no one reason why these attacks are happening, but there is an understanding that this issue will probably not disappear.
“We have more bears in more places, so the encounter frequency is going up, the probability of running into a bear is going up,” says Chris Servheen, U.S. Fish and Wildlife Service grizzly bear recovery coordinator, in the article. “We have grizzly bears occupying places they haven’t occupied in 100 years.”
It's worth reading Hull's entire article. Then, to help educate yourself and maybe calm your nerves, read Outside's helpful "How to Handle a Grizzly Bear Encounter" online sidebar. You know, just in case.