I suspect two other reasons the .260 didn't sell like Remington hoped were the .25-06 and 7mm-08, which had already been around for a while. Hunters who wanted more power than the .243 could buy a .25-06 if they wanted more zap with lighter-weight bullets, and hunters who wanted more bullet weight could buy a 7-08. As a result the .260 seemed to many a round that was going over already plowed ground.
Of course, that was back before so many hunters had problems running long-action bolts, or were aware of the incredibly enormous advantages of 6.5mm bullets.
