The Sega story is awesome. This is just a quick version, all iirc:
Before the Saturn, Sega had badly shaken the confidence of their consumer base (and just flat out pissed a lot of people off) with the Mega CD and (just as the Saturn was launching) 32X. With the Saturn, they not only made an expensive, difficult to devlop for system, but due to pressure from Sega of Japan they released it early (without decent software) and at too high a price. They did the same in Europe. £400 for the thing with 2 pads and Virtua Fighter.
To be fair, Sega of America knew this but the decision was forced on them by SoJ. SoA also weren't keen on the 32X, but SoJ made them do it, while pulling the limited software support they'd pledged as they focused on the Saturn (which they reportedly hadn't fully informed SoA about when they made them do the 32X thing).
SoJ also forced Sega to move away from the Megadrive about 2 years early, throwing away a good deal of profit and losing money on the Saturn instead.
For it's part, SoA prematurely announced the abandonment of the Saturn, greatly accellerating it's death and once again shaking consumer confidence. This also lead to a large period of absence from US (and European) retail space making the introduction of the DC even harder.
If the 32X hadn't followed the Mega CD, and had actually been propperly supported, it might have bought Sega time to redesign the Saturn propperly and been quite fondly remembered. For $150 it packed quite a punch for the time and price (cost £170 in the UK at launch though ffs). The Saturn was also impressive for a console redesigned pretty much from the ground up using stock/old components in the space of several months.