pokemon is really not luck based. That's why bad players never do well (except perhaps in this particular case).
I have three theories for this, and they're probably all wrong.
a) He got temporarily banned but is a really good player (likely from far away).
b) He got temporarily grounded before Worlds until this Regionals but is a really good player (likely from far away)
c) He is Jonathan Croxton's friend and picked up the game really fast.
EDIT: d) He is a divine being and we'll likely never see or hear from or about him again.
EDIT 2: That last one was a joke btw.
I have three theories for this, and they're probably all wrong.
a) He got temporarily banned but is a really good player (likely from far away).
b) He got temporarily grounded before Worlds until this Regionals but is a really good player (likely from far away)
c) He is Jonathan Croxton's friend and picked up the game really fast.
EDIT: d) He is a divine being and we'll likely never see or hear from or about him again.
EDIT 2: That last one was a joke btw.