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Paul Kimmage, an Irish amateur, turned professional in 1986 with the French RMO team. He rode as a domestique through three Tours de France, finishing in 1986 and abandoning in 1987 and 1989. He had resisted doping, then took an amphetamine injection before a post-Tour criterium, and in 1990 published Rough Ride describing the peloton's drug culture from the inside, which made him an outcast in the sport and launched his career as a journalist.
Doping in the peloton was not mainly a scheme by star riders chasing glory. It was rational survival behavior by poorly paid domestiques whose short contracts depended on visible results and on criterium appearance fees. When renewal hinges on performance and the rules are not enforced, the marginal worker cheats to keep the job.
The peloton enforced a code of silence in which denying doping to outsiders was the price of belonging. Anyone who broke it was treated as a traitor by the insiders, not as someone telling the truth. This let a practice that was known to everyone inside stay officially nonexistent, because admitting it was punished more than doing it.
Riders did not decide to become cheats in one step. Each line crossed, from vitamin injections to recovery products to amphetamines for 'unimportant' criteriums, made the next one easier to justify. The culture framed it as 'everyone does it' and 'it's only this race.' To understand how honest people join corrupt systems, look for this sequence of small, locally defensible steps rather than a single moral choice.