Short answers, pulled from the story.
Sega released the Saturn in North America on the 11th of May 1995, four months ahead of its scheduled September launch date. This surprise move caught retailers like Best Buy and Walmart completely off guard.
Hideki Sato supervised the project as director and deputy general manager of research and development. The team behind the Saturn had previously built the System 32 arcade board, giving them deep experience with high-performance game systems.
Sony allocated £20 million for holiday marketing compared to Sega's mere £4 million. By November 1995, the PlayStation had already outsold the Saturn by a factor of three in the United Kingdom.
The cancellation occurred in early 1997, leaving the platform without a flagship 3D title. STI disbanded later that year due to management changes at Sega of America.
Worldwide shipments from March to September 1997 dropped from 2.35 million to 600,000 units. North American shipments fell even sharper, declining from 800,000 to 50,000 during the same period.