He would keep fighting if he was innocent. But Lance knows that lying in court is a bigger problem than the actual doping offenses. So, rather than risk perjury and related charges, he can just stop fighting, characterize it as a witch hunt, and let the public decide what matters. At the end of the day that's the real question anyway. His place in history will be determined by the public, not the record books. Unless you are incredibly naive, his wins already have asterisks - making it official doesn't really change much on that score.