One takeaway I have from both the 2008 crash and the cryptocurrency mania is that it's actually very hard to create a financial system that is not mostly fraud and gambling.
There's a couple reasons for this. One is that people are greedy and I've even seen really honest people get weird around money. The second is that humans are extremely prone to falling for the alluring cognitive biases and fallacies behind gambling. A corollary of the second is that gambling doesn't always look like gambling and can emerge spontaneously in markets, but when it does it still runs on the same emotional and cognitive biases that make people go to casinos.
The line between fraud and gambling can get blurry too. Can you get away with it? Hmm... wanna bet? Every act of fraud is kind of a dice roll. Get away with some fraud once and the gamblers' fallacies start taking hold.
It's really really hard to organize a large scale civilization or financial system so that most activity is honest and/or productive. It's a constant Red Queen's Race against both intentional fraud and systemic failures.