: As the Ur-Didact said himself, I felt it left him mad. Corrupted. As logic
: corrupted and turned AIs, the Gravemind's invasion of the Ur-Didact's mind
: left him scarred. These scars changed his flow of thought and almost put
: him on edge in a sort of ways.

On top of the on top information, he would be somewhat aware inside the Cryptum and was meant to have access to the Domain, dwelling on the vast wisdom and knowledge left there by many generations of Forerunners, which would slowly calm his mind and "heal" him. This is evidenced by the Librarian mentioning in SpOps how he was meant to give the Janus Key to humanity and work with them to a better future.

Instead, the Domain was destroyed by the firing of the Halos, which left him with nothing but 100,000 years of his own madness to dwell on.