Chess960

anyone knows what is chess960?

The pieces on the 1st and 8th ranks are randomly distributed (black's position always matches white's though). This produces 960 possible starting positions. It's a much more tactical game that eliminates the focus on opening theory.

Is there official tournament made FIDE for this chess960?

There are chess960 tournaments, I don't know if they are official or not. I am guessing that FIDE is not involved as they would not be with other variants.

Does anybody know why this was invented and why this platform went along with it?

https://en.wikipedia.org/wiki/Chess960

Does not say why anyone would not want to play a game with worldwide appeal for over 400 years. What has it got to do with Chess? I would rather play real chess with the dice.

Quoted from the Wikipedia article:
"The random setup makes gaining an advantage through the memorization of openings impracticable; players instead must rely more on their spontaneous talent and creativity over the board. "

That's why it was invented and why many prefer it. It focuses more on ability and less on memorization.

Bobby Fischer was a weirdo. Memory is useless without understanding. Why is this fairy chess supported by this platform?

Yes, first FIDE-sanctioned edition was in 2019, with a very strong field:

2019 FIDE World Fischer Random Chess Championship

The 2019 world edition was FIDE-sanctioned. Wesly So, Magnus, Nepo and Fabiano were there. 

Chess960 gives many unique positions and makes you think from move 1. Variants are a great way to mix up playing the same 8 x 8 board game

Yes, fairy chess had a following in the chess magazines for the jaded chessplayer. Historically the game was played with 1 or more dice.

Chess960 does away with most opening memorization and in doing so forces a greater understanding of piece coordination. And it does it by focusing on chess ability without introducing the luck of dice throws.

Chess960 is supported by chess.com as it is a very popular variant of chess that many people (myself included) enjoy playing. 

Chess960 is a chess variant where each player’s back rank pieces are rearranged in a random order. It removes opening theory from the game as pieces are in different places each game. You can play it on chess.com as a variant on the website or select it on a challenge in the app.