No, not everyone "knows" about Cipollini doping. Most people (random folks who might just watch the Tour & nothing else) know Armstrong doped, know Pantani doped, know Ullrich doped, know their climbing times are "suspect". But sprinters from their era (Zabel etc.) or classics guys (Dekker etc.)? No.
The only non-GC rider who gained doping notoriety shortly afterwards was Cancellara with the widespread suspicions of motor doping & his suspect bike swaps in Paris-Roubaix.
Exactly. DQS are everywhere, winning trillions of stages, classics, criteriums etc. but on Grand Tours, they win punch stages & sprint stages whilst the GC guys earn the suspicions of the public.
Sadly, the myth in public perception endures whereby it's the GC mountain climbing/TT winning Tour winners who do the doping. So Cav, Alaphilippe & co are safe, for now.
I think people in Germany who know a few cyclists know that Zabel doped and he has pretty much vanished from the public, apart from being Rick Zabel's father.
About Cavendish: The story is great, but as unbelievable as it gets.