I'm in the middle of reading Kurt Eichenwald's 'Conspiracy of Fools'. When Enron management described all the innovative ways they were 'making money' they weren't kidding. They were creating it out of thin air with complex, mirrored in and out transactions of all types in every utility sector they could find, and no one (except Arthur-Andersen only occasionally) was there to call them out on it until it was too late. Reading about it, it almost feels like a .9 release of Theranos, where management was complicit and clueless at the same time.
Make sure to watch "The Smartest Guys in the Room" as well. While reading something well-written is usually more insightful than film, the interviews, recordings and internal marketing videos are priceless.
Management was not clueless. They were greedy, and they hired and built a greed culture.
I'm not aware of how Eichenwald got access to the communications he uses in the book, but in addition to, yes, the highly complex, dare I say innovative structures they created to temporarily satisfy Wall Street's demands, he also cites example after example of Fastow and Skilling doing or approving actions and special projects that had fundamental flaws that were certain to eventually implode - it's not like they were playing 5 moves into a game and getting it wrong occasionally. They were playing 2 moves into the game, often getting it wrong, and then covering it up with some equally flawed fix that in turn itself would later become a grenade. It's easy to argue in reading the book that they definitely weren't the smartest guys in the game, just the most audacious.