When Paramount made the decision to bring Gene Roddenberry and his universe back to television, there was no guarantee it would work. No sequel series to a television show had ever surpassed the original until Star Trek: The Next Generation. Today, fans at conventions can't help but notice how The Next Generation cast seems to truly adore each other, which is markedly different from the relationships of the Star Trek: The Original Series cast. However, behind the camera, the sequel series suffered a lot of problems, and it was up to actor William Shatner to unearth those early troubles.
Source：https://www.cbr.com/star-trek-the-next-generation-chaos-on-the-bridge-william-shatner/
