Nobody has ever shown that Cancellara was cheating there. Maybe he's just a monster. When Joop Zoetemelk casually disappeared from the front of the pack in the 1985 World Cycling Championship nobody could believe it because Joop was 40 years old. Nevertheless, he did it, and there was no stealth motor technology at the time.

So far, with cycling, P(discovered cheating later | outrageous) ~ 1. Some people will believe that when they go indoors the sun stops shining because there is no longer any proof. It's certainly a strict way to seek one's knowledge. Others have a different view.

I don't buy your comparison with bolt. This is just a video showing someone exploding? Happens all the time. They're riding at the limit for long, and then when one can't handle it anymore the difference is stark.

Boonen said himself that he was having no issues there. You could probably find that hill and estimate their watt output.

I wouldn't be surprised if Cancelaara is in excess of 1400w for short parts of that hill.

Yeah, except for Boonen is a sprinter and a hill climb even a short very steep one is probably the worst terrain for him. Cancellara isn't a climber but as a time trial specialist, he's a lot better suited for the kapelmuur than Boonen. And cancellara is better at descending as well.

Ah yes Tom Boonen, famously ill suited to the flandrian classics

Yes, Tom Boonen was ill-suited for going up an 18% grade.