Reply #1: You answered your own question.

[BzaDem]

There were 59 supporters of the Medicare buy-in before Lieberman reversed himself. (Ben Nelson later said he was opposed to it, but that was just because he knew it wouldn't pass at that point -- Ben Nelson actually was part of the group of 10 that negotiated the Medicare buy-in.) Lieberman (not part of the group of 10) reversed himself because he heard Anthony Weiner say something good about it.

Reid was so furious that he almost killed the bill. Luckily, cooler heads prevailed and the bill still passed despite Lieberman's intransigence.

But there will still be lots of conspiracy theory nuts who think that killing the Medicare buy-in was the Obama-instituted plan from the beginning.