Ask Master Chief a difficult question, and the super-solider lead of "Halo" often has an answer at the ready: "I don't know." From early on in the Paramount+ series, adapted from the sci-fi-inspired video game space fantasy, the scientifically enhanced human doesn't know much.
This is a video game trope.
Master Chief's fuzzy memory is a common conceit in games, one so cliched it's stunning that it still happens. Opening an adventure with a hero who has somehow had his recollections wiped is a narrative shortcut to do away with the disconnect between player and character: Why would we be instructing someone to seek out answers to questions they know the answers to?