Final answer:
Many members of Congress supported laissez-faire policies because they received money from big business.
Step-by-step explanation:
A secret reason many members of Congress supported laissez-faire policies was because they received money from big business. By supporting policies that favored business interests, members of Congress could receive financial support from corporations and wealthy individuals. This financial support could come in the form of campaign contributions or other forms of financial assistance. By aligning themselves with big business, members of Congress could also benefit from the influence and power of these corporations, which could help them advance their own political agendas.