he dumped nearly 500k no doubt bcos i have been watching the market last few days, selling 40k+ rapids each time, he kept selling even @2500, nobody had that much yet no time to mine it.
Is it possible to see coinmarket.io trade history somewhere?
If these were rough equal chunks one at a time, it's clearly him.
Otherwise it could be a chain-dump (as mentioned before) - early big buyers were panic-selling at a loss.