I do not know why he does it.
It could be that he and Jihan are just bluffing in the hope that the Core developers will come up with some sort of a compromise between them and the large blockers. It could also be that he and Jihan are looking to take over Bitcoin, where their 'crew' will form the main group of developers. It could be that they are just trying to push the price down for whatever reason by threatening to fork Bitcoin. Either way, they are working
against Bitcoin right now. Especially when you also look at how they are spamming the network with worthless transactions.