This is what's great about science. These two conditions have most likely been associated for awhile, it's just that no one thought to look for a connection until now.
The fine print to the article is that the patients studied were from an inner-city allergy clinic in New York, so this finding may not be representative to asthma patients as a whole. Also, no one is claiming that one ailment is causing the other. However, since they are statistically linked in this case doctors have something to look be on the lookout for.
What's causing this correlation between asthma and food allergies? There are theories, but no one knows for sure. It will take a few more studies, with carefully designed statistical experiments to get to the bottom of this.