I'm not sure why you think that Exelon didn't consider regulatory risk as one of the things that made it not make sense for them. It was certainly a large factor.
The idea that existing nuclear power plants are losing money because they aren't operationally competitive with oil and gas does not square with the facts. The total cost of running a nuclear plant is 30% less than oil and gas per kilowatt-hour. And if all our nuclear plants weren't 50 years old and saddled with massive overregulation, the operation and maintenance of a nuclear plant would probably be equivalent to running a fossil fueled power plant, which would cut ANOTHER 30% off the cost of nuclear because fuel costs of fossil fueled power plants are 4 times the cost of nuclear fuel per kwh.
https://www.eia.gov/electricity/annual/html/epa_08_04.html
And as for construction costs, you can see that the massive increase in construction costs in the early 60s and 70s was because regulation required enormous increases in staffing, which ballooned labor costs.
https://ifp.org/nuclear-power-plant-construction-costs/
And even so a nuclear plant should be expected to be profitable as long as you can manage to operate it for long enough without the government shutting you down (one of the major regulatory risks I mentioned).
Nuclear power plants in the past generally took 7 years to build and pay off in 16-24 years. While a natural gas plant can be built in 2 years and pay off in 8 years. Nuclear power plants are so cost effective tho, that if you can manage to run it for 17 years, you'll make more money than running a natural gas plant.
https://www.youtube.com/watch?v=UC_BCz0pzMw