well, he's definitely had more direct impact on the market, in terms of a daily trade response, than probably any POTUS that anyone can remember, over his ~2 year reign of incompetence. Overall...broader market factors are going to have the real impact.
Still, the type of shit he claims (obviously lying, boasting, whatever his intent), have such strong daily impact, literally swinging billions in cash from pocket to pocket on a daily basis whenever he pulls this shit, that it baffles me that the FTC hasn't opened an investigation into him regarding market manipulation, insider trading, and slew of other high crimes. ...One wonders, if one were to look, you can track a rather predictable group of people and funds that are consistently making out like bandits in those ~3 day periods on either side of a Trump market dump tweet.