I am pretty much this was because of fat fingers, but how an earth there's no security measures for this kind of thing? It's 2020 already and after seeing this kind of mistakes, i am pretty sure that ETH adoption is further away. Just one warning message informing about the possible huge mistake could have saved millions for this guy.
This is crazy, I just checked his address. He has more than $ 11 million in that address and he made a mistake with over $ 2 million for a small transaction. Surely he would have regretted letting this situation happen