The collapse of Enron was primarily driven by massive, systemic accounting fraud. Enron utilized dubious accounting practices, particularly mark-to-market accounting and the extensive use of off-balance-sheet Special Purpose Vehicles (SPVs) or Special Purpose Entities (SPEs), to hide enormous debts and toxic assets from investors and creditors. It was not caused by unauthorized trading (like Barings Bank) or unanticipated market moves (like LTCM).