Final answer:
Enron employees' 401k retirement accounts were decimated because they were heavily invested in Enron's own stock, which became worthless after the company's financial scandals and subsequent bankruptcy.
Step-by-step explanation:
Many current and retired Enron Corp. employees had their 401k retirement accounts wiped out when Enron collapsed because a significant portion of those 401k accounts were invested in Enron stock. When the company filed for bankruptcy in December 2001 amid revelations of widespread corporate fraud and accounting malpractice, the value of Enron's stock plummeted, essentially becoming worthless. Since the employees' 401k plans were heavily weighted towards Enron stock, either by their own choice or the company's encouragement, their retirement savings were severely diminished or completely obliterated.