2. But more modern and fuel-efficient
3. And air travel is just plain a bigger market these days than it was in the 1970s
4. As it's made by an American company, they hope to avoid the US protectionism Concorde was subject to.
Concorde failed because there wasn't enough of these people.
Eventually you run out of people willing to pay $10k a seat for this type of travel. Which is what happened to Concorde - after the novelty wore off, all you had was an extremely expensive seat.
I think British Airways could have kept the Concorde flying longer than they did if it were not for this incident:
https://en.wikipedia.org/wiki/Air_France_Flight_4590
which happened at a lower passenger*mile count than the 737 MAX accidents and would have required a Space Shuttle style shutdown-and-reform phase. Concorde's avionics and cockpit were completely out of date and fixing that would have been expensive.
It remains to be seen whether post-COVID wealthy travellers will subsidise BOOM development costs as opposed to not flying or continuing with smaller private jets as at present. Although Boom is “designing Overture to be the first post-pandemic airplane", they will need a massive investment to scale from the single-seat prototype (still to fly) to an operationally profitable vehicle.