Odin knows the future and knows it is bad. The poem Voluspa has a seeress tell him the course of Ragnarok, the doom of the gods: the binding of the wolf Fenrir will fail, the gods and their enemies will destroy one another, and Odin himself will be swallowed by Fenrir. His gathering of dead warriors into Valhalla is preparation for a battle he already knows he will lose, a strikingly bleak theology of a chief god who fights on without the promise of winning.
It is important to be clear about the sources. Almost everything we have was written down in Iceland in the thirteenth century, two hundred years or more after the conversion to Christianity, above all the Poetic Edda and Snorri Sturluson's Prose Edda, the latter composed partly as a handbook for poets by a Christian author. They preserve genuinely old material, but through a later, literate, Christian filter, and scholars weigh them against skaldic verse, place-names and archaeology rather than reading them as a pagan scripture.
That the cult was real is not in doubt: Odin (as Woden, Wodan) is remembered across the Germanic world, and his name still sits in the middle of the week as Wednesday, Woden's day.