The rising cost of fuel made Concorde into a Vanity project.
You have to bear in mind that up until quite late in the Concorde project most of the world's leading airlines had options on a Concorde fleet. The industry truly believed that the future of passenger air transport would be supersonic, which is why Boeing themselves were skeptical that they could sell the 747 as an airliner (it had been designed as a freighter for the US military, but lost that contract to the Galaxy).
If you wanted a supersonic airliner, Concorde was the only game in town. The TU144 had a hopelessly short range and the US SST had got no further than a wooden mock-up. Unfortunately the prospect of hundreds of Concordes on the world's airline routes brought about the banning of supersonic flight over land around 1970 (so very late in the Concorde program), because of the sonic boom.
About the same time, the cost of oil (and therefore fuel) rocketed. But perhaps the most significant factor by far in sealing Concorde's financial doom was actually Boeing selling the 747 as an airliner; it brought about a fundamental change in the airline industry.
Wide bodied airliners enabled airlines to reduce the seat / mile cost, and therefore target a customer base who previously were not considered wealthy enough to pursue. The focus of the industry changed from luxury and speed, to economy. And economy has been the industry driver ever since.
That killed Concorde's chances of financial success, either in its original form or as the enhanced 'Model B' (which was of course never built). It found a niche market on the North Atlantic where the 14 production aeroplanes served that small but profitable market (for privatised BA at least - not for pre-privatisation BA and maybe Air France) for 27 glorious years.
Of course, with only 14 commercial airframes produced most of the development and some of the production costs were met by the British and French taxpayers. And I'm pretty sure my dad didn't disapprove of his tax pounds being spent on that beautiful white bird!
Financial disaster, sure. But so was the US Apollo space program. But both stem from a time when we did magnificent things just because we could - before the accountants started running everything.