Museeuw's wins in the Classics came from a broad number of factors (in addition to the admitted doping).
1. Having a sponsor that lets the team concentrate on the Classics and build a team around that goal. Look at 2001 Paris Roubaix, where the Domo Farm Frites team took 1, 2, 3, and 5 of the top five. 2004 Ghent Wevelgem when most of the finishing 20k was lead by 6 Quick Step Jerseys. (Just ask Hincapie about having a sponsor who doesn't give a toss about the Ronde or Paris Roubaix. Prior to 2006, he's rarely had a teammate to help him out - if you count Hoste's attack as helping him out.)
2. Ability to read a race. Know which breaks to chase, and which to let escape and run out of steam. Know when to work with other teams and when to shut them out.
3. Bike Handling - Whether he was doped to the gills or not, Museeuw and several of his team-mates seemed to fly above the cobbles, and accelerate better in the worst of terrain. It wasn't the racing pigeon EPO that allowed Museeuw to keep his bike upright as he powered through the mud in the 2002 PR.
4. Equipment Prepartion / Luck - Except for JM's untimely flat in 2004 PR, Museeuw's boys whether on Mapei or Domo Farm Frites, or Quick Step have usually been able to avoid untimely punctures and disintegrating steering columns and the like.
I was disappointed to know of Museeuw's charges years ago when they surfaced. His public admission actually gains my respect (as he could have continued to deny). I respect the bitter pill that Museeuw has had to swallow far more than the **** river of denial flowing frombelievetyler.org and flowdfairnessfund.org .