Olbermann was a huge success at ESPN where he teamed on nightly SportsCenter shows with co-anchor Dan Patrick. He perfected his own quirky style of Groucho Marx-like one-liners while narrating highlights of the day's sporting events.
Fox Sports had a budding network of their own but their version of a sports highlight show was drawing yawns so they did what any competitor would do when they can't measure up - they stole the star talent of their rival, signing Olbermann to a huge contract. However, without the wisecracking deadpanning Patrick as his sidekick (and some slick ESPN writers who probably provided half the jokes) Olbermann's new show also bombed. While I didn't watch his Fox show, his ESPN stint wasn't outwardly political any moreso than ESPN's typical fare.
Fox had another problem with Olbermann that they weren't counting on. Keith is blind as a bat. The Los Angeles-based Fox Network was in a dilemma because Olbermann's eyesight is so poor that he cannot get a drivers license. (Makes you wonder what Connecticut-based ESPN did for him - chauffered limos?)
MSNBC, meanwhile, was desperate for on-air talent (it's desperate when you hire the likes of Joe Scarborough, no?). Thinking that Olbermann could recapture the old magic, NBC hired him away from Fox which was ready to unload him anyway. The Peacock gave Olbermann his own show and that's when Funny Keith evolved into Hateful Wacko Keith. Now, he considered himself important (too many sportscasters wish to be taken seriously as news reporters in the same way Playboy models wish to be regarded as serious aspiring actresses) - too important to be restricted to mere sports. But at least in NYC, he could always take the subway to get around.
It leaked out from Fox also that Keith is a rather thin-skinned guy (like many liberals in the media) and is high-maintenance. I'm sure, deep down, he's resentful that NBC is shifting him back to sports and it might be a precursor to dropping his MSNBC show either in hopes that Keith will break his contract or just to salvage some value out of his contract.
I must say his early efforts on SNF have been unfunny, at best. And NBC won't have any use for Keith after January, 2009, particularly if a Democrat wins the White House. When your whole schtick is dreaming up wacky Bush conspiracy theories, who's going to want him around once Bush is out of office?