I think I'd vote for Francesco Conconi, who first made a name "preparing" Francesco Moser to the hour record in 84: Was hired by IOC in 1990 to make a fool-proof drug test for EPO, invested that money in the research necessary to make a fool-proof EPO mixture, and then made a fortune making sure just about the entire peloton was doped beyond all limits in the nineties. All the while lying about it to the IOC and UCI, saying that he was almost there, and that he just needed a little more money, thus making sure he was getting a steady income from the top of the sport, too. Meanwhile, no-one else got to have a go at it, and there were many more qualified scientists available, and they didn't get an EPO test until 2000... And obviously, finishing it all off, he was found "morally guilty" by an italian judge in 2004, however he couldn't get a sentence because the case was to old, meaning he is now a rich, retired doctor. And you can't forget his students Cecchini and Ferrari...
So there you have it: Inept leadership to the extreme and one evil doctor can really screw a sport up. I think we are just now getting back to the level pre-EPO, when guys would still cheat, but it was still possible to win the tour clean.