How can I recover my folders uncrypted after closing a vault?

Ah, ok. No that’s not possible. You can only decrypt your files with Cryptomator system. Either the Cryptomator app, or (if you want to access your files directly in OneDrive) with 3rd party app cyberduck, which has the Cryptomator technology included.
(See here: How do I use Cryptomator without local sync?)