Armand De Las Cuevas began working with Dr. Ferrari in 1991. Even though EPO became available earlier, the people who took it tended to wake up dead. It wasn't until the Italian trainers determined how to properly use it for athletic performance that individual riders began to really reap its benefits. That coincided with the rise of people like Bugno and Chiappucci.
When Gewiss rode away from the field in the '94 Fleche Wallonne it became obvious that all the other teams had better cowboy up, or they wouldn't be able to compete. That appears to be the time that team supported EPO use spread through the peloton.
The reason Indurain never gets any flack because he left the sport before the crap hit the fan in 1998. He conveniently retired the year that hematocrit testing started. All the top riders during his reign were using EPO. Look at the list of contenders we know were doped: Bugno, Chiappucci, Zulle, Pantani. Riis, Rominger, Tonkov, Berzin, Gotti, Ugrumov, Virenque, De Las Cuevas, etc. In order to believe that Indurain wasn't doping you would have to believe that he was so vastly superior than everyone else, he could beat the best in the world after they had increased their hematocrits by anywhere from 20 to 50%. I don't think that is believable. If I remember right, Indurain started seeing Dr. Conconi very early in his career, maybe even when he was still an amateur; that would have been the right after Conconi finished blood doping Moser to the hour record.
Doping was so prevalent during Indurain's time, how can you single out any one rider? You can get pissed off that Lemond's career fell off a cliff as soon as the other contenders started to get access to EPO, though. Riders like Lemond and Hampsten got screwed.
During the 1998 scandal there were calls to cancel the 1999 Tour until a plan could be put in place to clean up the sport. Armstrong came along and was siezed upon as the new clean face of the sport, a role he played to the hilt. For a while it looked like the anti-doping measures might be working. As top riders continued to get busted, doping rings were uncovered, and tales like Jesus Manzano and Philippe Gaumont's came out it became obvious that the sport was just as dirty as it used to be.
Most other pros are smarter than Armstrong and do not to portray themselves as saints when it comes to doping. They will make a diplomatic statement instead of challenging the press to prove it. As evidence began leaking out that Armstrong was not any different than the riders in the 90's, all his doping denials were like waving a red cape in front of a bull.