Personally I think that is just one very intelligent trader. I don't think he intends to send the price down to 5k sat then buy more and lose 40 BTC but he could, and wait a few weeks/months for it to return to 15k for a larger profit, or just pull the order and wait for a higher value, there is no rush to make money when you hold that much BTC. You don't lose BTC until you sell! I wonder which of those things will happen, and the last option could be project death but we will find out!
If you think otherwise maybe you should sell