From the luxury of our armchairs we can quarterback until the cows come home, but the people up front on the day were human, and beset with all the frailties present in humans. The task is to take the lessons of what went wrong, and remove those slices of cheese, with out apportioning blame.
Actually, I think most of us here to a greater or lesser extent can understand Collins's actions in terms of how he came to do the things he did. But understanding the man's actions doesn't mean that his actions were right, or justifiable. Trotting out lines like "armchair critics" and "we need to learn from this and remove slices of cheese", then having a group hug before retiring to read
Daughters of Erebus simply isn't good enough. Hempy's photo says why better than I can in words. 257 people with families and legacies all died in that photograph. They deserve better. Learn from what went wrong, of course; but implicit in that process is some aportioning of blame.
And several of us here having looked at all the facts closely, strongly believe that even without the benefit of hindsight, better could reasonably have been expected of Collins (and Cassin) on the day.