More than a thousand Amons each committed "Theft."
With "His" numbers, as long as "He" wasn't extremely unlucky, there would always be a few who would've succeeded. Furthermore, The Fool's potion was ownerless, so it wasn't difficult to steal.
While carrying out the "Theft," Amon removed a particular seal on "His" body, allowing the Apprentice and Marauder Beyonder characteristics to release their powers of convergence.
This was rather effective towards The Fool's potion, allowing Amon to increase "His" success rate to the greatest extent.
However, all the Amons ultimately failed.
This was because a new rule had appeared on the Trunsoest Brass Book:
"Acts of theft are prohibited here!"
In order to deal with the awakening Lord of Mysteries, Amon had weakened all the seals here and helped the Trunsoest Brass Book escape the "Fooling." It could now have a limited number of effective rules for a brief moment amidst its repeated cycles, but now, this had adversely affected "Them."