The idea is that a large part of the electorate in the US doesn't want the economy managed at all. Trump certainly isn't advocating for free markets, but he does offer a viable alternative to increasing state control over our economy.
It's pretty crazy to claim that providing Delaware corporation law, bailing out Wall Street, funding the IMF and World Bank, maintaining the neoliberal trade regime, and acting as one of the world's major tax havens isn't managing the economy.
If offering tax breaks to a company to get it to offshore fewer jobs (but not all) is not state control of the economy, then what is it?
Tariffs were the first major thing the first US congress implemented to ensure domestic manufacturing could be established and compete with what were up until then cheap imports.
The question is to what end will this be done, and will it be effective in reaching that end?