Trump's presidency was followed by a statistically significant increase in stock prices,(*) which climbed parabolically during anticipation of tax cuts and consequent economic stimulation. Even if Trump's agenda proves to stimulate the economy long-term, at this moment in time, and since February 2018, investors are less confident in their prior rosey economic forecasts and so prices are falling toward long-term 2009-2015 support, which held closer to real GDP growth.
However well Trump's agenda fulfills its promises will determine which of these possible trajectories the future holds.