The product was the Cadillac Allanté, a two-passenger sporty car styled and partly built 1987-93 by Pininfarina, an Italian coachbuilding firm. I'm not sure what General Motors' rationale was for this. It probably could be looked up someplace, but I haven't the heart to do so because what matters is that it was a mistake that was obvious to many at the time, me included. According to data in the Wikipedia entry on the Allanté, production over a seven-year run proved to be around half of what was expected on an annual basis.
Since Pininfarina was a firm well-known to sophisticated car buyers, GM touted the fact that the Allanté was indeed designed and the body built by it, rather than Cadillac. That was supposedly a big plus factor. But the coin had another side. If Pininfarina was so wonderful, that implied that Cadillac stylists were not as good. Therefore, the styling that the rest of the Cadillac line sported was not first-rate, something for potential buyers of prestige cars to ponder.
Problems, problems. The final problem, so far as I am concerned is that the Allanté's styling wasn't outstanding. The design was mediocre.
Reduced to its essence, the design is something close to a brick-shape with three character lines extending all the way around. The upper one coincides with the top of the tail light assembly and almost aligns with the top of the grille and headlamps. The second one aligns with the lower edges of those front and rear features. The lowest such line is painted red and isn't aligned with any other feature. The only serious relief from this horizontal theme is a slight fender line dip along the cockpit that transforms into an upwards kick between the rear of the door and the front of the wheel housing.
Perhaps the intent was to have the Allanté seem dignified, as would be befitting a Cadillac. Instead, the result is boring. At least Cadillac management learned not to repeat the mistake in the 20 years since the project was abandoned.
* Actually, there also was the case where Nash hired Pinin Farina (himself) to provide a design for the 1952 full-size Nash line. Advertisements stressed his contribution, but automobile historians tend to agree that much of the production design originated in the Nash styling studio. Around that time, Nash also marketed the Nash-Healy sports car, a low-volume model that also had some foreign roots. But Nash was not an industry leader as was the case of General Motors and its flagship Cadillac brand.