One of the permanent deacons at my parish is also a professional magician.
Oh, my! Is his assistant Johnny Eck? That is seriously the only way I can see this working. Wow.
Advanced Muppeteering is my guess. That’s the answer for the old fashioned saw a man in half trick, and I didn’t see the lower half do anything that couldn’t be accomplished with that (or, the upper half either, the surgical mask hid the face well enough).
This is an edited version of the full trick. If you really want to know how he did it (I know that takes all the fun out of it for some people) there is a magic tricks r evealed video that discusses how.