I think it's probably because I was there for it. His construction of the narrative, while better than many (including many straight journalists) ends up sort of falsely casting people into hero/fool/villain roles that make the book work as an entertainment, but don't fully hold up.
It's a decent book, and a decent movie (kudos for one particular scene where I recognized data from the actual LoanPerformance database) I actually prefer the movie Margin Call for more accurately capturing the feel of the crisis from inside a bank.
But wasn't the point of the Big Short to show the perspective of people "outside" the mainstream who made big bets against the system/banks? Not surprising then that it didn't really show what was happening in the banks themselves.
No, the book is very different from the movie, I'd say it's almost the opposite in that it was mostly narrated from the perspective of the banks.
Another compounding factor is people often assume the message is "banks bad" but it's more "oh this system was so complex that any one individual did not understand the impact of their decision(s), much much more than everyone/anyone was playing super fast and loose from their particular perspective "
It's a decent book, and a decent movie (kudos for one particular scene where I recognized data from the actual LoanPerformance database) I actually prefer the movie Margin Call for more accurately capturing the feel of the crisis from inside a bank.