They almost pulled the plug on the e-bodies for 72, but decided to cut production costs to the bones and see what happened with sales. They already had planned to build the convertibles for 72 but axed the idea at the last minute. The 70/71 convertible on Mannix had already been converted over to the 72 front and rear design because at the time they still had plans to produce the convert in 72. I think people tend to forget how bad things were getting in the 70's all of the way around. Poor economy, poor sales, high insurance costs and lousy construction. By 1979 the Mopar dealerships were closing left and right and if not for the government bailout under Lee Iaccoca, Chrysler would have ceased to exist before the 80's. I used to drive around Houston, Tx in 1980 and there were boarded up Dodge and Plymouth dealerships everywhere. No one expected them to survive.
In a nutshell, the 71 had far too many expensive parts and was far too expensive to build and be profitable.