It was a fast plane, but a poor design. They spent wads of money
to build and maintain them, then junked the entire fleet. It was
noisy and very fuel inefficient. That forced the fares so high that
they weren't able to compete with better planes from multiple
countries.

"Bad design" is debatable. Supersonic planes are inherently inefficient, and
the Concorde (which was actually a British-French design -- hence the name)
was expensive from the get-go.

You can't say it wasn't able to compete with other planes, because the
Concorde was the only supersonic transport. Even without the fatal accident,
the Concorde would have eventually gone out of business, as there just
weren't enough rich people or business who needed to zip to Europe and back.