Well, with the little info on liquid used and quantity, I'll take a stab at why.... When you add yeast to granulated sugar, the yeast begins to absorb moisture from the air surrounding the yeast. If there is no liquid to suspend the sugar in, the yeast feeds until it dies, normally from alcohol poisoning. The specific gravity and strain of yeast determine how long the yeast feeds and when it dies, so to speak. Some yeast tends to live longer or is more tolerant of alcohol than others, such as champagaine yeast which can live in concentrations of up to 18% by weight of alcohol. It sounds like the yeast was not 'pitched' into a slurry that was high enough in liquid to support good yeast activity. Like I said in the beginning, this is just a guess.