There were many flaws in Market Garden but it has to be said that the all-important ingredient of luck wasn't always on the Allies side.
It was certainly a stroke of ill fate that Field Marshal Model, one of the best German generals, happened to be on the spot. His reaction was a model (pun intended) of flexible response.
Secondly, it was another unlucky break when the Arnhem battle-plan acquired from a shot-down American officer fell into German hands within hours.
I'm not sure if the presence of 2 Panzer Divisions near Arnhem (although at 30per cent strength) was down to bad luck entirely. As Jet says, the Dutch resistance had forewarned them.