My strongest memory is of an almost-new silver-painted Charger that had caught on fire a few blocks from the Penn campus early in my grad school days there. After the flames and dark smoke dissipated, all that remained to be seen was the rusted body shell that lingered for a few days until it could be hauled away. Not an exact metaphor for the market fate of the model, but it never sold well, as this Wikipedia entry indicates.
That aside, it was an attractive car fated to compete with other attractive entries in the hot late-1960s American sporty car / muscle car / pony car market segment. My guess as to why it was a comparative failure is that (1) it was too large, (2) and its styling didn't proclaim that it was a gutsy machine. A redesigned Charger was launched for the 1968 model year.
Charger II concept car that was a 1966 Charger with a few extra styling touches. Differences included the grille, hood and, as shown above, extended fender tips. Standing beside the car is Chrysler styling boss Elwood Engel.