Why the fuck did they retire the Concorde
A few reasons. It was always expensive, so it was sensitive to any economic issues that effect the airlines. But there was also a serious accident. An aircraft, not a Concord, lost a strip of metal that had been manufactured incorrectly on the runway. When a Concord took off a little later, it's tire hit the strip and instantly exploded. Aircraft tires explosions can make semi truck tire explosions look like a joke, and the Concord's tires were under more stress than traditional airliner tires because of the immense takeoff speed required. It's airframe was designed for efficient supersonic travel, not high lift at low speeds, so it had to be screaming down the runway to get airborne. This increases the energy of any flying debris when a tire explodes. Some pieces damaged one of the 4 engines. Others punctured the fuel tank. The fuel quickly burst into flames. Other engines started to give out because of flames and/or tire debris. It crashed soon after, killing people on the ground too iirc. No one survived. It was found that the tires and fuel tanks would need extensive work to become safe. Iirc this may have been done, but at great expense and it added weight which made the fuel burn higher.
After this, 9/11 happened. This was apocalyptic for many airlines, and the following years saw many bankruptcies and mergers, which resulted in the big 4 we have today: Delta, American, Southwest, and United. All Concord operators retired the aircraft, as it wouldn't become economically viable again for several years.
Now multiple companies are researching how to bring supersonic flight back. NASA is testing a design to eliminate the sonic boom, allowing flight over populated areas again. Hermeus is designing engines for such an aircraft. There are a few others but I can't remember.
I'm sure I got a few details wrong but that's the gist of it. I work in aviation on the technical side of things so I enjoy this stuff. Like you I watch all the Mentour Pilot videos (the Rikieta "pull up" intro was amazing). If you ever need an aviation correspondent just hit me up.