It seems that the concept was to create a small car that had luxury touches, an idea that has been tried with varying degrees of success in the years since. One way to do this is to focus on the interior, using quality materials (real wood, for instance, rather than cheap grades of plastic). Where the Mayflower's stylists went wrong was to assemble upper-crust exterior styling details on a small, short-wheelbase chassis. Those details originated on large, long cars such as custom body Rolls-Royces and didn't seem legitimate when scaled down to Mayflower size. Another possible error was to add the new (at the time) feature of the flow-through fender line.
Aside from trying to put the proverbial gallon into a pint jar, the Mayflower stylists encountered a problem not understood at the time: It is difficult to graft a razor's edge upper body on to a more modern lower body, a case in point being the early 1980s Cadillac Seville (scroll down on the linked article).