But a couple of things were kind of glossed over.
1) The GFC was probably made much more severe by these bets. It is difficult to short mortgage loans. There are derivative methods like shorting banks, but it is very hard to short a basket of loans. In order to do that, Wall Street set up a huge amount of derivative CDOs so that these guys could short the loans by agreeing to pay the interest on these bundles of loans into these derivative CDOs until a default. There was not a natural buyer of these CDOs in such huge size, so risk-averse investors were sort of gulled into buying them based on their AAA ratings. They should have known better, but the Street wasn't exactly laying out all the facts to these people.
The end effect was that the very worst bundles of loans (think strippers in FL owning five houses) were referenced probably 20-30...100? times across different CDOs. In the normal course of business, a default on a mortgage will cause some loss on a loan, but there will be a reasonable recovery when the property is foreclosed upon and sold. But, since derivatives are zero sum, these losses were magnified 20, 30, 100 times across a wide swath of CDO owners. The gains on the other side were concentrated in the pockets of a few speculators like John Paulson and Michael Burry. So, you could argue that there was no aggregate increased loss to the economy. But the wide distribution of the losses and concentrated nature of the gains meant that the impact was felt more severely (there are only so many Hamptons mansions for these guys to buy).
2) The bets themselves were insanely huge and concentrated. All of these guys failed basic risk management. If the crisis had been delayed by even a year, most of them would have gone bust and we'd never have heard of them. They were on the hook to pay, say, 8% interest on the gigantically leveraged positions until an event of default happened on each loan. I can't tell you how many times I have seen people with the correct macro call who have missed the boat because of the way their bets were structured. Theses bets were ticking time bombs in their own portfolio and the concentrated risk was really insane. But it all worked out for them in the end, and people still care what Burry and Paulson think even though they haven't done anything useful for almost 20 years.
If you like that one you should also check out Margin Call.