SASless, the rather purple language about hanging Generals doesn't help the discussion much. I notice that they are British. This was an Allied Operation that went wrong, no doubt thanks to poor leadership, but that leadership was Allied. The Bridge too far/late wasn't at Arnhem but at Nijmegen. It should have been taken by the 82nd on Day 1. It wasn't, which allowed the Wehrmacht to occupy it and the town of Nijmegen instead. It wasn't until XXX Corps tanks got there that it was fully in Allied hands, despite the Little Omaha bloody sacrifices of the 504th. Tanks need infantry to advance, and Horrocks's infantry were now in Nijmegen town clearing out German troops that needn't have been there in the first place. To leave them there would have allowed them to sever XXX Corps advance in two.
Of course it was a gamble, but it was a gamble that required a non-stop advance by XXX Corps straight to Arnhem. Nijmegen stymied that and cost the Operation's success more than anything else in my view. Yes about Ultra, Resistance, and Photo Recon evidence of Panzers but those Panzers needed time to react to stop the advance. They got it thanks to Nijmegen.
There is a tendency to judge outcomes in black and white terms. Eisenhower carried a letter around on D-Day to take full responsibility should it fail. He might well have had to do so were it not for Fortitude and Allied Air Power. Even so, it was a damn close run thing!