system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How large banks "bet" against their own investment products. How do banks sell investments opportunities and then profit when they fail?

I'd like to know more of the predatory practices some banks engaged in that led to them profiting in a matter that affected regular people.
gpt
They bundle together a group of investments and then essentially buy 'insurance' so that if they fail they get covered by the insurance.

The insuring companies would do this because they believed these investments were solid and wouldn't fail. So when they did fail, and we all found out later it was because the banks were making trash investments and didn't care because they made money either way -> those insurance companies were sca-roood!