Why AE2's failure would not stop the Gallipoli landings

If AE2 had not made it through the Dardanelles, would it have changed decisions at the opening of the Gallipoli campaign?

Probably not. It might have made the minefield seem stronger, but the campaign was already too far in motion for that information to stop the opening decisions.

A failed passage would probably change the Allies' estimate of the Dardanelles defences. They would infer a denser and more effective minefield. That warning arrives too late to halt the broader opening moves because the landing plan and supporting activity were already in motion. Intelligence can arrive after institutional commitment has become too difficult to unwind, even when it should influence planning.