This explains a lot.
... my favorite explanation comes from Jonathan Chait of The New Republic, who theorized that Lieberman was able to go from Guy Who Wants to Expand Medicare to Guy Who Would Rather Kill Health Care Than Expand Medicare because he “isn’t actually all that smart.”
It’s certainly easier to leap from one position to its total opposite if you never understood your original stance in the first place, and I am thinking Chait’s theory could get some traction. “When I sat next to him in the State Senate, he always surprised me by how little he’d learned about the bill at the time of the vote,” said Bill Curry, a former Connecticut comptroller and Democratic gubernatorial nominee."...
Lieberman is a dull man who's not that interested in understanding the world. He's dull enough to be profoundly corrupted by his insurance company donors, yet still imagine that he's an honest man.
A lot like George Bush Jr.