To a casual observer, the writing has been on the wall for sedans for some time. Why would I want to buy a sedan when I could buy a crossover SUV with the same fuel economy for the same price?
Ford has been on top of this trend - they announced they are discontinuing ALL sedan production earlier in 2018.
Car manufacturers come out with new "generations" of vehicles every 5-10 years, so change in production methods is part of the industry. Why can't American manufacturers adapt?