Because the transfer of the King Kong trademark from RKO to Cooper did not comport with these requirements, according to Nintendo it was an invalid transfer. Nintendo challenges this lineage, maintaining that trademark rights, such as those Universal claims in King Kong, cannot be bought and sold in the abstract, and that they may be transferred only by means of a controlled licensing program or along with the product they identify or the assets or goodwill of the business that developed them. Then, on December 15, 1976, Cooper sold these rights to Universal, and it is these rights which Nintendo is alleged to have infringed. On December 6, 1976, Judge Real held that Cooper, not RKO, owned the rights to this trademark. Let me stop you right there: Universal alleged trademark infringement on the King Kong trademark and lost mainly because it was determined the King Kong trademark had never been sold Universal in the first place. Nintendo itself won the fabled Donkey Kong lawsuit by proving that Universal itself had forfeited its rights to the King Kong IP prior to that (therefore, they sued in bad faith and lost). (You might want to look up the concept of " orphan works" where not only does the copyright holder do nothing to "protect" their ownership of that copyright but they cannot be located and are sometimes not even aware that they own it - and despite all that they still retain that copyright for decades.)
Modern copyright (particularly in the United States) is impossible to lose no matter how neglected it is. That's true of some forms of intellectual property (like trademarks) but it's not true for all of them. Property, intellectual or not, is something that, if the owner neglects to protect, can be lost.