Lance's fundamental error was thinking that Landis wasn't mentally strong enough to go through with the nuclear option. Large swaths of the public are buying into this belief, too, without stopping to consider the reality. It's easy to respond to one's own bitter disappointment, anger and sense of betrayal (responses to Lance's being revealed to be an unrepentant doper) with misplaced transfer of all those negative feelings to Landis - especially when one's hero (LA) is carping about how Landis (and LeMond and everyone else)_ are bitter, jealous, losers, failures, mentally-unstable alcoholics.
People do themselves a disservice if they stop with that and don't ask, "well, is floyd really mentally unstable? CAN he handle this?" And of course he can - because nothing is on the line for him except the chance to recapture the sense of being "ok" with himself.
So for Floyd, telling the truth and admitting to the pantheon of doping wrongs brings him release, closure, an unburdening, etc., whereas for Lance it represents the destruction of his entire self-created cynical myth.
There's no strain at all on Floyd in comparison to the last four years' lying. He gets better every day. The opposite though is true for Lance - each day brings him one closer to a final reckoning.
And if he's innocent, he should be thrilled to have the chance to prove it in open court!