Your last sentence is on the mark, as far as Cadillac was concerned. There was a power renaissance at every foreign luxury car company in the 1980's but Cadillac had invested heavily in small economical cars with zero sex appeal. Had Jimmy Carter won a second term those tiny generic and underpowered 1980's Cadillacs would have been correct in the marketplace. With Reagan came national strength and economic greatness and buyers chose cars with those optimisms in mind. As a kid I couldn't believe how my favorite car brand fell from greatness to near nothingness so fast.I can't imagine who the developers of the "Duntov GT" thought the buyers of this car would be; maybe some sinile Mafioso chieftan; I mean even little old ladies from Pasadena had moved on to "hot" foreign cars by the mid-eighties. Bro-ham is absolutely right, no young up and comer from the executive class would have been seen dead in a Cadillac of any kind in the mid-eighties. Some of my friends still had their late seventies Fleetwoods with the big engines and would never have considered trading them for an eighties model. I still had my '76 Seville in 1985 cause their wasn't anything more interesting ( I had an 82 XJ6 as well) to behad in the marketplace. The Eldos were nice looking but even slower than my Seville. The 1980's were just a waste land for those who enjoyed powerful good looking cars.
This Brougham was the only Cadillac platform the Duntov concept could have been based upon at the time. The tragic mistake of Cadillac in the 1980's era was failing to recognize they needed to keep a big Cadillac built V8 in the rear drivers, the 368 with a 4-speed auto would have been great, and the 90-92 updates on the Brougham should have come out in 1983 or 1984 with a whole new updated rear drive following in 1985 or 1986 including a traditional big Cadillac engine and some knock your pants off up to date and class leading Cadillac styling.
I wish Cadillac would drop the current pug nosers they seem so intent on building and instead do some glamorous long, low, and lovely cars that will truly get people excited about dreaming of and aspiring to own Cadillacs.