It was probably quite clever, but I’m not sufficiently knowledgeable about to topic to understand.
The electronic debice ,the Capacitor, acts much like a bucket as far as DC is concerned. It charges up (Fills) then the current stops when it reaches full. Maximum capacitance. DC no longer appears to flow.
AC on the other hand changes direction many times a second so the Bucket never actually fills, (Fill, empty, fill, empty) ,so the AC appears to pass clean through the Bucket.
All I know is that the capacitor from one of the old-style TVs could still put 700 or mover volts through you after many minutes of being powered off.
Capacitors is powerful stuff.