Agreeing with Seamus's Post;

The Allies also weren't aware of the actual size and strength of the Dutch SS, and Regular Wermacht operating in the area, which was much larger than anticipated, and hadn't expected much in the way of heavy armor, from their intelligence reports.

Instead they dropped "light" expecting similar results as they had during Overlord, what a terrible surprise for the British 1st, not only had they dropped their supplies right into the German's hands, but most of it would have been relatively useless against the Brunt of Army Force B, that they managed to hold out for so long against such overwhelming odds was a testament to their training, skill, and courage.