1. Tariffs directly take money out of the coffers of private companies and move it into the government. Private companies therefore have less money to invest.
2. Tariffs are a tax on economic activity and therefore suppress it. This causes companies to want to hold more cash and invest more conservatively. Major changes take appetite for risk, which tariffs reduce.
In addition, the arbitrary, legally questionable way in which this particular set of tariffs has been imposed means they are not affecting long-term corporate planning. Instead most companies are seeking to just “wait them out” while issuing hollow press releases with big numbers they think the president wants to see.