I'm reminded of a saying an old boss of mine had (stated somewhat less colorfully than he did); "Hindsight is 20-20....................if you had an eye in your butt you'd be perfect!" It's easy to second guess their decisions looking back.
Perhaps the best lesson is that successful marketing decisions (actually all business decisions) really aren't that easy, which would help explain why so many people fail in business and so few prevail. Second, and only slightly behind, when the private sector makes a big mistake while spending it's own money, they pull the pin as soon as possible. If this were a government idea we'd still be funding it (I guess the diehard Edsel guys would like that).
A couple years later the Falcon hit the market, probably had a bunch of market planning and engineering effort expended too, and is considered a "success", or at least not a colossal failure like the Edsel. But it only lasted 10 years (or really only 9 if you ignore the Fairlane based finale). On the other hand, the Falcon spawned the Mustang, which, despite the Mustang II, has been a long term success. And the Mustang probably didn't have near the market study that the Edsel had. There is something to be said for gut feel...............but it has to be a savvy gut.