Answer: The SEC claimed that they didn't act because they were understaffed and overwhelmed
Step-by-step explanation:
Markopolos repeatedly informed the U.S. Securities and Exchange Commission (SEC) about Madoff´s massive Ponzi scheme. In 2000, 2001, and 2005 the SEC disregarded his claims or merely gave his evidence a cursory investigation.
The SEC has claimed that at the time they didn't respond properly due to a lack of staff. It´s also believed that some filings were ignored because Markopolos was working for a competitor to Madoff's firm.