Why did Libby attorney Ted Wells say he was going to put Libby and maybe Cheney on the stand and then backtrack? It didn't help him with the jury and it sure didn't wash down well with the judge.
Here comes the crazy speculation part: Wells threw a bomb at the administration with his open. He talked about Libby being the "fall guy"; he talked about a broad conspiracy. It was in Wells' power to embarass Cheney and the administration badly. With that leverage, perhaps he negotiated a secret pardon deal with the administration that would make sure Libby never spent a day in jail. All of a sudden, Libby and Cheney aren't testifying anymore. And all of a sudden, all the conspiracy stuff from the opening just dissolves away.
Wells has a reputation as one of the best of the best. He's too good to be changing strategies erratically in mid-trial, unless there's a good reason. Since the prosecution case was so solid, this might well have been the best way to defend his client.