For athletes like him who earn a lot of money, yeah, this is just a lunch money for them and with that kind of emotions and reaction, it seems that he just enjoyed the game.
Sure, it is not really big money for Neymar, so it won't be a serious problem for him. But his strange reaction implies he is unsatisfied with the result. Most people only enjoy the game when they won or experience an interesting game. However, it is a bit difficult to feel happy if they lose a big amount of money. Well, £900k or €1M isn't a big amount for Neymar but it is still a big money for sure.
I don't know what game he played that cost him $1M in an hour, obviously that's bad even though he has another suitcase in the safe.
According to the source, it may be Poker.
He loves Poker. But in the article, we can't see a detailed explanation about the game which make him lose $1M.