defrauding isn't synonymous with stealing- he did take the money under false pretenses. if I come to you for investment in my cool new startup that does distributed crypto machine learning ai for entertaining bored housecats on the blockchain and come back a year later having sextupled your investment in money from illegal arms smuggling, you've still been defrauded.

Except derivatives that almost sank the country for a few decades in 2008. For some reason selling derivative where it's incredibly difficult or impossible to know what securities they are derived from isn't fraud.

https://www.thebalance.com/role-of-derivatives-in-creating-m...

No, he defrauded his investors and lost their money.

He later managed to come up with money from another source to pay them back, but that doesn't erase the fraud that he previously committed.