Surprised no one has mentioned it by now but those are stock example maps that ship with the unreal engine sdk, infact IIRC though might be wrong even the pickups aren't their work, the only thing they have done is model and animate mario - all the movement code, etc. are example blueprints.
i.e. 1min 23 in is the map from the elemental demo
https://www.youtube.com/watch?v=dD9CPqSKjTU