The most likely explanation is that the government got to him somehow. The government can make someone an offer he can't refuse. He has family; he might be afraid someone in his family will have an "Accident" if he doesn't play ball.
Here'a an example of a sane scientist saying wacky things years after she blew the whistle.
Lauren Moret is a rational scientist in this video.
http://video.google.com/videoplay?docid=-3626298989248030643
Now she says the US government may have caused the earthquake in Japan and some other wacky things.
http://www.youtube.com/watch?v=5WxmeOqYtB0
http://www.youtube.com/watch?v=MrtOblmLZ08
People don't change like that. I'd bet the government got to her; she has a daughter so she probably has a grandchild or two by now who she doesn't want to have an "Accident". She looks a little ill-at-ease in the YouTube video. The government has ways of getting to people and making them say what they want them to say.