It also had a three person crew, and post 9/11 was the start of structurally higher oil prices, both of which were a death knell.
The true nail in the coffin was the development of the lie flat business seat, which meant that you could cross the Atlantic in three hours in a plush but cramped seat, or spend less money to sleep for six on a redeye and arrive well rested. At that point three hours was not a compelling enough time savings, but the Concorde also didn't fly far enough to do routes where the speed resulted in more significant time savings, like on transpacific routes.
London doesn't even require a red-eye from NYC--or actually from Boston/Washington although it's a very early star--on a conventional jet. I've done it pretty regularly. Not pleasant but I can get to London in time for a late dinner.
The true nail in the coffin was the development of the lie flat business seat, which meant that you could cross the Atlantic in three hours in a plush but cramped seat, or spend less money to sleep for six on a redeye and arrive well rested. At that point three hours was not a compelling enough time savings, but the Concorde also didn't fly far enough to do routes where the speed resulted in more significant time savings, like on transpacific routes.