Backers of bimetallism knew it would "dilute" the value of existing currency (i.e., would cause inflation, with subsequent known negative effects). They did not "miss" that, or overlook it; they accepted it as part of a tradeoff. They knew there would be some pain at the outset, but believed that the eventual outcome -- of increasing the number of people who could turn metal into legal tender at a favorable rate, and breaking up some of the power of established wealthy interests -- would outweigh that pain through resulting economic mobility and wider-spread prosperity.

Hence the argument for "trickle up", effectively, as opposed to "trickle down".