In 2017, as a dying wish, Choi asked Lee and Kim to continue on with the LK-99 research but asked to not publish it until they understand the theory behind it.
They founded a lab and collaborated with other scientists in the field and Kwon was one of them.
4 months ago, Kwon left the lab and two weeks ago Kwon leaked the paper. The paper Kwon leaked only listed Lee, Kim and Kwon as the authors and excluded other collaborators. Some suspect Kwon excluded the other collaborators because Nobel prize can only be awarded to three people at most. A few days after the leak, Lee & Kim hastily published a paper with four more authors but not Kwon.
Then a few hours later a paper was published with six authors (without one of the original three authors), ostensibly by the core team that has been working on this.
There should be much more detail on the Internet if you search for it.
Nobel prizes are capped to 3 people, and the speculation is that the rogue person published early to try and ensure they were one of the people that received it. No reason for infighting like that if you know it's a hoax.