now, I have a question, do you think the man is entirely at fault or someone should also be responsible?
Sounds like he knew something was wrong, because why did he make the same size withdrawals and gambled it all away in a few weeks? If he is addicted to gambling and has no more control over his finances than it's understandable, otherwise I think it's wrong. If I would ever get a large bank transfer by mistake I would never think about starting to gamble with it heavily. Even if the law wouldn't be clear on that and there could be a chance that I can keep the money. What if the money was send by mistake by some criminals and they find out my name and adress? I am sure they wouldn't be so understanding and accept an apology. And what if the judge orders him to repay all the money, including the one he has lost? It could ruin him financially forever.
If you are someone who doesn't really like to get involved with some possible risk of getting yourself fucked up on the future then it's just sensible that you shouldn't spend the money which aren't yours so that you won't really be having problems later on because even if you do put up into your mind that it isn't your fault but still you would really be finding yourself in big trouble on spending money or funds which aren yours.
You aren't that dumb that it wasn't wrong in the first place because who would be the one on expecting to get big cash or funds directly into his account without any possible source?