Beck was attempting to break out of the conventional Republican mold set by Rush Limbaugh and Sean Hannity. For a while, the puppet shows and conspiracy theories were amusing, but once the novelty wore off, Beck had no substance to fall back on. There's a market out there for something other than the conservative-movement mulch shoveled up by Hannity and Mark Levin, but it requires more depth than Beck is capable of.
Beck did try to break out of the mold, and if I had to choose I'd take him over Hannity any day. But he was too sloppy with his facts, and too prone to letting all those Discover the Networks-style conspiracy theories about the left distract him from the much more substantial foes of liberty in the center. Politics aside, his skills as a broadcaster are immense—he may be as important an innovator in TV as Limbaugh was in radio, sort of an Ernie Kovacs for the Cleon Skousen set. I'm sure he'll land on his feet.