One Explanation for Recent Stock Market Whipsaws

I've been mystified by the massive swings upward in the stock market whenever Trump makes a sttement backing off his tough tariff talk. After ten years of listening to Trump throw out stalling lines whenever he feels cornered, no human investor would believe him. So why would the markets take ot seriously? Remember Obama's birth certificate? Whenever asked Trump would say, his investigators would have something in a few weeks, and that "They're finding amazing things"  (they didn't). Or Infrastructure Week? It was always a couple of weeks away (it never appened). 

On tariffs, when the markets began to seriously freak out, he said that the administration was already in talks with China to lower them, only to be contradictd by his Treasury Secretary, Scott Bessent, a little later, who said talks hadn't begeun (and also by China, which also said that talks hadn't begun). 

So, the mystery is why very smart and cynical investors would believe him when even ordinary people recognize that this is as his standard waffle when things turn against him?

The answer might be that humans might see through his lies, but the headline-reading algorithms that dominate a significant portion of stock trading can't. They simply see the headline, read it as "trade war less bad" and react accordingly. This is not reassuring.