Trumpism will expand its base of believers and practitioners if it is not strenuously opposed, just like Nazism, Communism, Capitalism, Liberalism, and every other -ism. Trumpism is an idea. Ideas can only be defeated through the greater popularity of a competing, alternative idea.
Ideas have currency because of the moral values which underlie their motive, reasoning, logic, and their intent. Ideas can also sometimes have currency due to the experienced reality of the outcomes of actions based on them, but that comes later (it takes time) and is frequently overlooked through selective perception and/or other cognitive biases.
Still, there are concrete steps which can be taken and are not token echo chamber participation.