What accounted for the tremendous rise in the profits of the american financial industry, from less than 10 percent of total business profits in the 1950s to more than 40 percent in the 1990s?

Financial deregulation was a big part of why profits soared during these years. With businesses feeling as if they had more freedom to use their profits as they saw fit, they were able to increase technology, innovation, and therefore, their overall profit margins, instead of having to use those profits for tax purposes.