On one obvious interpretation of "Go ask the people who actually predicted it in advance", he ought to go and ask the authors of isekai novels what they were thinking. Perhaps all of those books are secretly concealed advice to true-Dead people like him, with the actual logic of their reasoning having been classified by the Keepers as an infohazard.
Othrem permits himself to think this obvious thought, that it may pass over him and through him, and then set it aside for a time until after he has tried to take things at face value first.