no point for u to know anyway its not like u can ever achieve a brillaint move your a cockroach play like one okay and be blessed someone like me came to show yall reality
How rare are "brilliant" moves according to chess.com's analysis?

The free analysis hides "great" and "brilliant" moves. Maybe its a good marketing strategy. ie. "people want to hear they're great and brilliant".
now it doesnt

Me too, I just castled and it was a brilliant move like WHATTTT
https://www.chess.com/analysis/game/computer/391279320/review?move=40

what brilliant move is this, bro i just castled and review said that it was brilliant
https://www.chess.com/analysis/game/computer/391279320/review?move=40

Over 3100 games, I've gotten around 20-30 brilliant moves. So, they are uncommon, but not "rare" in a sense. It's hard to calculate "rarity" or "probability" because brilliant moves aren't random. But, yes, they are "uncommon".
I touch on Chess.com's brilliant algorithm and classifications in my blog post:
https://www.chess.com/blog/Ethanchock7/how-to-get-your-first-brilliant-move-the-complete-guide

https://www.chess.com/analysis/game/live/144133915738/analysis?move=62 brilliant move at 400 elo btw
Chess.com's brilliant moves are comparatively uncommon since the engine only recognizes them when a move is both highly effective and non-obvious, usually a deep tactic or unexpected sacrifice. They are not merely "great" moves; they are ones that exhibit inventiveness or ingenuity that even skilled players might overlook without careful consideration.
Was this written by AI?
None of it is true. A computer can't even comprehend things like "non-obvious" or "unexpected".
Instead, the definition is simple: "A sacrifice that's good".