WASHINGTON—The Trump administration’s revamp of a powerful consumer-finance regulator is reaping dividends for high-interest lenders: The agency is easing its oversight of the industry after closely scrutinizing it during the Obama era.

Under its new Trump-appointed leadership, the Consumer Financial Protection Bureau recently called off a four-year investigation into World Acceptance Corp., a South Carolina-based lender that targets subprime borrowers with short-term, small-dollar loans carrying annual interest rates of...