He didn't really explain himself in the post per se, but in ensuing comments in the discussion thread Williamson makes clear that he doesn't buy the idea that Kocherlakota was persuaded to change his mind by evidence. Rather, he states that the only good theory he has for the flip-flop is that "ambition collides with economic science." In general my impression is that people who run around talking a lot about "economic science" are generally engaged in an unscientific level of self-puffering and BS. But that aside, it would be interesting to engage in a little psychological science. Having put forward the theory that Kocherlakota is only pretending to be persuaded by evidence, Williamson doesn't offer any theory as to what the nature of the ambition is. What job is he angling for?
Here's what I think about ambition. I think that if I were an ambitious monetary economist who believed in good faith that the current course being pursued by the FOMC will be ineffective in boosting employment and is likely to produce a troubling level of inflation, I'd be shouting that from the rooftops.
Why? Because when we're mired in inflation, all the whores and politicians will look up and shout "save us!" and they'll be shouting at the people who called it right. When Milton Friedman warned that the naive Phillips Curve economics being pursued by the Federal Reserve in the late-60s and 70s would lead to ruinous inflation, nobody listened to him. Until suddenly they did listen to him and low and behold Milton Friedman was super-famous. Developing a correct analysis of the situation and then explain it is obviously no guarantee of success in your career. But all else being equal, it tends to help. That said, sometimes things aren't equal. But I wonder what it is Williamson thinks isn't equal here? What job is Kocherlakota angling for? And how will pretending to believe something he knows is wrong help him get it?