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

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".