[prerok]

That's an interesting take but I think it's unlikely for two reasons:

1. In any case you view it, it's not trivial, which was the statement in the note. If it were, the effort to publish just for n=4 would be silly, because it would take equal effort to just publish for general case. That he withheld the proof just to mess with people is highly unlikely.

2. I definitely do not make private notes in my books just so that maybe somebody later on would pick up that book and wonder whether I had indeed discovered the secrets of the universe. I definitely do not write "challenges to the community" there.

[DoctorOetker]

In what note by whom was it stated that FLT is trivial?

[prerok]

https://mathworld.wolfram.com/FermatsLastTheorem.html

[DoctorOetker]

That URL does not substantiate any claim by anyone that FLT was trivial to prove.