They don’t have idea about it and even though some of them believe to have idea that the future value will increase, they’d hope to get some of them back by buying bitcoin back or after winning big in this bets, they can use the profits to buy back and hold. The more fact about this is that the value was also insignificant and was still within the price range they can risk, so they don’t mind about it. Just wait, in many years to come, if Bitcoin reaches a million dollar per one as envisioned by many, the price people use today to gamble will become a very big amount then that would not be used by most gamblers to risk on just a game. As time changes, so is the condition of everything does. This happening in the future and looking back today won’t be a surprise again.