Why did the SEGA Dreamcast console fail?

My mate had a Dreamcast when I had a PS1 and I thought the graphics on the Dreamcast were fabulous compared to the PS1, and every bit as good as the PS2 when that was released. So why did the Dreamcast fail and was taken out of production? It seemed a console ahead of its time, the graphics looked superb, and a really wide range of games as well. So what went wrong?