How can I remove all my downloaded YouTube videos in the YouTube iPad app in one go?
In the YouTube iPadOS app, tap on the account profile picture at the top right of the screen, tap on Settings, scroll down to the Offline section, and tap on Delete downloads item. You'd be alerted stating that all downloaded videos and playlists will be deleted from this device.
Tap on Delete button to delete all the videos downloaded and saved for offline viewing on the device.

Tap on the account profile picture shown at the top right of screen to access your account.



Scroll down on the account sub-window and tap on the Settings item. Scroll down on the Settings screen and tap on the Delete downloads item.


In the pop-up window that appears, tap on the Delete button to delete all offline videos in one go.


This would instantly delete all the offline videos in one go and and you'd be able to re-claim the storage space on your iPad.