During the tug of war for the control over the Sifara Castle both The Fool and The Error were loosing control over their very being.
They both have let go of the control over 60%. Amon felt threatened he tried to make an escape but The Fool didn't let the opening slip .
When faced with a Supernova in His face Amon knew he was going to loose. So what if had a million avatar when faced with The Fool any logic is meaningless.
The moment before his eminent demise The Error though " well looks like I failed. Even though I can survive this . This world is getting very boring" in that moment Amon let himself loose control to The Celestial Worthy to 99% .
Using his almost perfect control over the Sifara Castle and Adam stabilizing his condition Amon only had a split second to execute his almost insane plan by sacrificing his everything.
Amon Fooled the very concept of universe then created a Error in it's very fabric then created a Door and Grafted himself to the first unfortunat sole that he sensed stole his identity,life,mind, future but he destroyed the Fate . Amon wanted new life but being restricted by Fate was some thing he didn't want .
Yes, this was his insanity. He was trying to excape the universe The Oldest One . Just for what? Because he was bored.
This was an impossible task but he had done it. He had control over Sifara Castle so he just Stole the Chaos Sea from his father.
When Sifara Castle and Chaos Sea merged He got the glimpse of The Oldest One who is absolute yet very definition of contradiction.So what was impossible became possible.