Cloudy with a chance of meatballs

I'm disturbed that the movie of Cloudy with a Chance of Meatballs changes the book so much. Of course they had to add characters, to lengthen the story and give celebrities voice-over work, but the filmmakers also changed the point of the story. In the movie, a scientist's invention runs wild (partly because of the overindulgence of Chewandswallow's mayor?) and then they face the consequences.
In the original book, of course, the natives of Chewandswallow rely on the weather to provide all of their food. When the weather goes crazy, it is through no fault of the townspeople. The book even mentions that the leftovers are gathered up to feed the town's dogs and cats, and then the remainder goes to the ocean to feed the whales and other aquatic life.
Was this message - that the environment can go crazy on you, enough so you have to leave it forever, through no fault of your own - too much for the executives who signed off on this movie? Did a marketing group decide to add a greedy, overeating mayor as a cautionary tale, or as an excuse for the audience to laugh at the fat guy? Sadly, I'll never know, but it's clear that the movie version reflects 21st century concerns about what people have done to the environment. It's more comfortable, perhaps, for an audience to be shown the familiar 21st-century environmental message than to be reminded that Mother Nature can be a very cruel parent.