Trump did take credit for every single DOW increase since his election, so it is only natural that people attribute a fall to him too, as a 'gotcha' moment of sorts.
However, as an economist, I do not think it is just normal fluctuation. The increase came -at least in part- from tax-cuts being promised etc so any information that decreases the likelihood of those happening has a negative impact. Mind you, that is just cause and effect, without any judgment.