When I was a young man, Sega was in the console industry. They were making and selling machines that play computer games, but at the turn of the millennium they had some bad luck and decided to leave the console market and just make games.
I Blame the switch from 2D to 3D partly for their bad luck because the rules for fun are different in 2D and 3D. In 2D it is all about completing the level and scoring points and avoiding death.
In 3D gaming fun is more about exploring and going on quests or missions and finding things. When SEGA first went 3D, their games were rigid and inflexible. They litterally made their 2D games into 3D ones. They were in my opinion very linear.
Like all extinctions in this world, there is more to their back luck than that. They eventually cleaned up the problem but the other games consoles had their best run at that time. Xbox had Halo, PlayStation had a powerful hand held, and Nintendo had many party games for the family and groups.
I think the last Games console they made was called the "Dreamcast" and I think it was in many ways the best console but the previous console they made, Sega Saturn had damaged the companies image and poisoned the marketing for the Dreamcast.
I often wonder what it would be like if Sega was still in the console industry today. If they didn't make those bad decisions. Perhaps in an alternative reality or in the future Sega will be making games consoles once again.