His time at Channel 4 was OK. Not as good, or rather interesting, as his predecessor Jeremy Isaac's, but he was the last Channel 4 boss who really maintained the mandate to be different that Isaacs had established. Grade's successors let C4 slide into a morass of Big Brother, property porn and make-over shows.
But he was brought back simply because the BBC was in a bad way, and he was seen as a media profesional who could sort it out: the director general and the chairman of the board of governors had both been forced to quit after a row with the government over the BBC's coverage of the government case for going to war with Iraq (a row which, officially speaking, the Blair government had won, but which did so much damage to its reputation that it arguably came off even worse than the BBC. Remember those old silent comedies which end with the warring neighbours both standing in the ruins of their homes? A bit like that...).