Late in the film “Lance,” a documentary that depicts the ascent and the crash of disgraced cyclist Lance Armstrong, the subject recalls the disappearance of his lucrative sponsorships. These deals — with a massive market value and a perhaps more important intangible value of keeping him in the public eye as a figure of rectitude and hard work — were in some sense his life’s work, and they vanished after his 2013 admission that he had used illegal doping throughout his cycling career.