One rainy afternoon early in February 2018, a procession of consumer experts and activists made their way to the headquarters of the Consumer Financial Protection Bureau in Washington to meet Mick Mulvaney, then the bureau’s acting director. The building — an aging Brutalist layer cake, selected by the bureau’s founders for the aspirational symbolism of its proximity to the White House, one block away — was under renovation, and so each visitor in turn trudged around to a side entrance. Inside the building, Mulvaney had begun another kind of reconstruction, one that would shift the balance of power between the politically influential industries that lend money and the hundreds of millions of Americans who borrow it.