IP patents, abused. Again.

In cause you haven’t heard, Immersion Corp successfully filed suit against Sony Corporation alleging IP infringement for controllers that vibrate as synchronized with game data. The result is an injunction against further sales of the PS2 platform, a future licensing agreement, and $90 million in damages.

Never mind that Sega’s Outrun had vibrating controllers in 1986, which was well before Immersion Corp. existed.

Why didn't Sony present this Prior Art in the proceedings? If they did why wasn't Immersion Corp's patent voided? What on earth is going on here?