Doping was an excuse. Lemond lost 3 years of competitive racing with his hunting accident and by the time his body recovered he was no longer competive and that is clear from the results. Lemond was one of the last of his generation of seasonal racers. They would take it easy during the falln and winter months and then starting in early spring they would work to get back in shape for the coming season.
What made Lance such a great racer was that he trained 12 months of the year. Armstrong was the number one rated triathete under the age of 19 in the United States in 1988 when he was only 17. It is also naive to think that only a few bicyclists used some way to enhance their performance as this has been going on for as long as there has been professional racing. The concern arose initially with the death of British rider Tom Simpson in 1967 on the Tour de France when he experienced heat stroke and heart failure from dehytration that was the result of his taking amphetimines and alcohol.
At this point we have athletes that cannot use an over the counter decongestant but are allowed to use a asthma inhaler which greatly improves performance. Athletes use low oxygen tents to up their red blood cell count and use transfusions to add more blood before a race and other means to have an edge over competitors who are doing the same. Lance says he was clean but we have to take his word for it as it means when he was racing the drug testing was far less prevalent and far less sophisticated.