I just don't know what to think in this case. Was the owner drunk or having some health issues? Maybe the wallet and funds were inherited by someone who has little knowledge about Bitcoin and was trying to make his first transaction. It could also be a human error from someone knowledgeable. I think is ethical for the F2Pool to refund the funds after deducting some expenses, doing that will make their reputation rise in the industry. As the story unfolds I just hope it has a good ending and that the funds are returned to the owner.
Most wallets do not let you specify the absolute fee of the transaction, and only the fee rate in satoshis (per vbyte), so a truly careless person would have to somehow shove 10 zeroes into the fee rate or had automated the transaction, because this is bordering on the line of recklessness otherwise. I don't see how someone can accidentially pay $500k in fees otherwise.