The original concept was a gamble. The dice roll came up snake eyes. But it was stupid pride that turned a bad beat (one could argue that it was bad luck, or astute placement, that the Nusret managed to lay a line of mines that ended the naval campaign) into a slaughter.
The root cause of the whole thing was Winston Churchill.
Churchill was a gambler. I actually didn't know this. I typed it in before I googled for it (https://www.telegraph.co.uk/books/what-to-read/no-more-champagne-churchill-and-money-david-lough-review/). But if you look at Churchill's life and career, it seemed like a reasonable guess.
Gallipoli was no different.
It was an audacious gamble: high stake, high risk (with a very low chance of success), but potentially very high reward.
One could argue that the original concept was brilliant, take a bunch of old battleships not fit for combat against the High sea Fleet and sail them up the Dardanelle, through the sea of marmara, into Istanbul, and force the surrender of the Ottoman Empire.
But the strategic importance of the Dardanelle was so self explanatory to all, it has been heavily fortified for centuries and centuries.
So the brilliance of the original concept was entirely a matter of whether you share Winston's passion for gambling or not.
The challenge to the strike fleet of nearly a 100 ships with over 30 capital ships was, it must traverse 36 miles through the Dardenelle, a narrow and heavily mined stretch of water between .75 and 4 miles wide with Ottoman forts on both sides.
The fleet never actually got very far. While the mass of heavy entente naval firepower did demolish some ottoman forts at the mouth of the strait, they were never able to silent the guns harrying the minesweepers. So when the entente lost 6 battleships (3 sunk 3 headily damaged) on march 18, 1915, the officer in charge, John de Robeck, called off the attack.
Winston Churchill wanted to double down and sent more ships to replaced the lost vessels, but the renew attack never happened.
It is worth noting that the anglo-french fleet never even breached the first line of the 10 layers deep mine field.
It should also be noted that even if they could breach that, there was nothing to say that the ottoman could not simply set up more mines and prepare more guns further up the strait.
And it should be further noted that even if all that happened and the battered fleet reached Istanbul, there was no guarantee at all that the ottoman would simply surrender to a naval fleet with no ground troops. And there was nothing to say that the Ottoman couldn't close the straight back up, and trap the whole invasion fleet in the sea of Marmara.
So conceptually, a naval attack up the Dardanelles was an ill considered gamble that didn't pan out.
But the true tragedy comes after the initial failure to force the Dardenelle by sea.
After that it was decided that the strait couldn't be breached without securing the land side first.
A reasonable observation, but now the Entente was just double downing on a weak trash hand.
And what followed was 9 months of pointless slaughter, with ANZAC forces trying to take the ottoman hills overlooking the landing beaches. One side had superior naval firepower, but the other side had geography (the mythical high ground)...
The causes of failure were pride, stupidity, a passion for glory, and an obstinate refusal to admit defeat.