The tax cuts that Trump was obsessed with were never a good idea. Their benefits were heavily slanted toward corporations and the wealthy. But they were also an unnecessary stimulus to an economy that was already overheated. That was all that Wall Street needed to justify dumping stocks whose valuations were out of sync with reality. His tax bill also produced new debt in excess of $1.5 trillion. That makes investors nervous about rising inflation and interest rates.
Finally, when an economic stimulus is used at a time when it isn’t needed, that means that it won’t be available in the future when it might actually be useful. So investors are looking forward to a future market correction, or even a bear market, and the government will have no tools to respond or mitigate the damage. Therefore, many are getting out now and moving their assets into safer investments or cash. And none of this would be happening were it not for the greed and ignorance of Donald Trump and his allies in Congress.