One thing that I have never quite understood is why the later injected and supercharged Coupes and HPEs were withdrawn so quickly, not just from the UK market where the rust legend had already set in, but across Europe. I know that the Beta range was by then over ten years old and had never had more than tweaks in terms of body designs, and the Berlina looked dated when the ugly Trevi was introduced, but to my eyes the Coupes and HPEs still looked good alongside early 80s designs. It may have been production costs and plant capacity as the Delta was taking up most of the money by then.
By the early 80's coupes were considered old hat. Everyone wanted hot hatches instead, and the Delta HF Turbo and GTie fulfilled that market.
Also, when Lancia withdrew the Saloon and Trevi it wouldn't have made commercial sense to continue making the common parts for the Coupes (suspension, subframes etc.), and in any case the production capacity would have been needed for the more up to date Deltas, Themas and then Dedras.
When the coupe market was re-booted in the 90's Fiat and Alfa snaffled the sporty designs; Coupe and GTV respectively, while Lancia got the Kappa Coupe, after Fiat bottled mass producing the Hyena. The rest, as they say, is history.