If you read all the books covering the history of the deregulation of the regulated electric industry in the US, their reasoning was clear. Many years ago, under regulation (and still for those areas of the US that aren't in a market), it was the job of planners to determine the load growth and to build enough supply to meet demand and get a steady ROR. We did really bad at this in (I think it was the 80s), so there was a lot of pushback in making customers pay for generation they didn't need. At the same time, combined cycle plants made it possible to finally de-monopolize the generation side of things. The theory was the free market would be more innovative than the regulated utilities and less wasteful.
"Made possible" also meant that coal burning plants were obsolete and we needed to restructure the generating system so they could go out of business without making the utilities go under.
So much in the energy literature looks like a clock that stopped. For instance you still see cost estimates of advanced combustion systems from the 1970s that have been carried into the future without adjusting for inflation and changes in technology.
People still compare nuclear power to coal but they quit building coal plants circa 1980 for the same reason they quit building nuclear plants -- the capital cost of the steam turbine is an order of magnitude more than a gas turbine, so even if you get the heat for free a current generation coal or nuclear plant is going to struggle to compete against the power plants we've been building since the 1980s.
The US built coal plants in the 1990s and even in the 2010s. These last ones started construction in roughly the years 2003-2008, when US natural gas prices were elevated and (many thought) due to go up even more:
Coal's brief renaissance was halted by a triple-whammy of lower gas costs (from shale), lower wind costs, and lower solar costs. It's soon to face another whammy: falling grid scale battery costs. I don't think that the continental US will ever build another coal generating station. But that happened more recently than 1980.
A big part of that is the 70s/80s inflated destroyed capital budgets and reduced capital spend.
Regulators always have a bias towards rate reduction. Once the deregulation movement set in, power generation became a fat hog ready to be exploited. In some cases, investors even got to use tax free municipal borrowing facilities.
