Complex sentence: Pecora's investigation produced evidence of irregular practices in the financial markets that benefitted the rich at the expense of ordinary investors which led the United States Congress to pass the Securities Act of 1933 and the Securities Exchange Act of 1934.
Split into simpler sentences: Pecora's investigation unearthed evidence of irregular practices in the financial markets that benefited the rich at the expense of ordinary investors. Spurred by these revelations, the United States Congress enacted the Securities Act of 1933 and the Securities Exchange Act of 1934.