From la Gazzetta dello Sport:
GdS: You saw the devil approaching (MvdP) as you rode in Hell:
Colbrelli: "Yes and no, in the sense that he was decisive in giving the final knock-out blow to Van Aert, who I saw was in difficulty. Allowing him (Van Aert) to come back on would have been risky. The Dutchman pulled super hard, allowing me to stay away (thus implying he had been aggressively on the attack before MvdP caught up)
GdS: Grande Italia, but Gianni Moscon was so unfortunate:
Colbrelli: "He was so strong. Perhaps we would not have caught him without the two mishaps he had. At Roubaix you need a day when everyghing goes perfectly..."
As we witnessed in the race itself and as Colbrelli tells us, therefore, Colbrelli rode an agressive race to then play off MvdP at a critical moment to his advantage. It's not Colbrelli's fault that MvdP apparently has the need to overdo (strafare) things, evidently either owing to overcondifence, in which case he sins of hubris, or an incapacity to ballance effort with astuteness, in which case he suffers from stupidity. At any rate, Colbrelli simply smartly played off MvdP's strength, a feat that deep into Roubaix is iteslf no mean task and shows you have the legs to win. Then after Moscon was caught (the moral winner of the day as far as I'm concerned), Colbrelli went to the front and accellerated again, which seemed to put even MvdP briefly in difficulty who going full gas was lingering at three meters behind the Italian's wheel.
MvdP after the race said he was absolutely dead on the track just before the sprint and just hoped that his rivals were more dead than himself. Obviously they weren't quite so empty, with just that bit more reserve to keep ahead in the sprint for the finish line. To be fair, it was truly tough for MvdP, who was not riding just to leave Van Aert behind but catch a flying Moscon, who only through the cruelty of fate likely didn't stay away for the win. The Dutchman, however, races like he has the responsibility to take on the race full gas no matter what. While undoubtedly admirable, this clearly is not always the best tactic, especially when you have strong rivals who can play off your strength, but also your getting carried away.
Moral: Colbrelli was no wheelsucker, just smart; MvdP was in a tough position, not helped by his uncontrollable enthusiasm to always go eyeballs out; Moscon was poised to arrive solo, were it not for the fact that Paris-Roubaix is the one race where you can have the best day of your career, and apparently are going to win, when anything can happen that screws you over.