According to "Nice Tiger", the only person Shere Khan has ever been nice to was his grandmother, who seems very old in the episode. When we come to the contemporary Jungle Book setting, said grandmother must be long dead… which could have contributed to make Khan the way he is in the movie.
Everyone's friendships will eventually wither and die. Baloo, Bagheera and Hathi won't become friends again until years later and Shere Khan and Kaa, and arguably King Louie too, will never repair their friendships with the others with the "Born to be Wild" VHS explicitly confirming Shere Khan as he claims "the past is the past" when Baloo tries to remind him of their friendship. Louie on the other hand is the Narrator of the VHS and explicitly calls the others his friends.
