While the popular macOS sees updates nearly annually now, there was a time where Apple struggled for years to get a major update out.
macOS is based on technologies developed between 1985 and 1997 at NeXT, a company that Apple co-founder Steve Jobs created after leaving the company.
In 1996, Apple announced that it would buy NeXT for $427 million. The deal was finalized in February 1997, bringing Jobs back to the company he had cofounded. Jobs became de facto chief after then-CEO Gil Amelio was ousted in July 1997. He was formally named interim chief executive in September. In March 1998, to concentrate Apple's efforts on returning to profitability, Jobs terminated a number of projects, such as Newton, Cyberdog, and OpenDoc.