Because it was a smart gamble, if you just look at it in terms of talent. Charlotte made a surprising run to the playoffs, and they probably thought that, with LeBron leaving the Heat, that the east would be wide open, and that they were maybe only a player away from really making some noise. On paper, Stephenson fills pretty much all of their holes. Clearly, they underestimated the impact that he would have on their chemistry, but it's not hard to understand why they thought it would work.