Re: As a Canadian
Monty's ego and desire to be "first over the Rhine" caused him to completely ignore the advice from the Admiralty that Antwerp was utterly useless unless he also took the approaches. Instead of ordering them captured from the very weak German forces at the time, he had them charge hell for leather towards the German border. The Germans recognised this and reinforced the approaches and it took months to capture them.
Meanwhile, Antwerp was useless even though it had been captured with the docks intact. The allied forces were on the end of a very long supply line from Normandy via trucks and as a result were out of fuel and munitions and stuck on the German border. Antwerp operating would have meant one of the biggest ports in Europe could be used to deliver munitions etc. to forces faster and in much greater volume.
This two month delay in getting Antwerp opened gave the Germans time enough to reorganise their forces (hence the victory in Market Garden) and allowed them enough time to kick off the Battle of the Bulge.
All in all, not the mark of the "strategic genius" that Monty liked to parade himself as. Indeed most of his "genius" can be attributed to him taking over the Eighth Army at the time when Bletchley Park had started having a great deal more success in cracking Enigma. Post war his time as Chief of Imperial Staff showed up just how out of depth he was.