As the author states in one of the last paragraphs, "it may simply be that as more people are doing CrossFit, more people are being injured."
Every physical activity has inherent risks. And having no physical activity at all is perhaps more dangerous than anything else.
What surprises me more is that while the injury rate for CrossFit is estimated around 3 per thousand hours and ranging from 1.4 to 5.5 for triathlon, it goes as high as 2.5 to 12.1 for running.