This is unusual: a highly divergent set of indices. You don't see that much, typically they're in far more agreement - but the broadest market (S&P 500) is flat, the NASDAQ tanked, and the smallest sampling (DJIA) was up sharply. Even the curves aren't the best fit.
This was two things, and shows the occasional problem of relying on something like the Dow for your only market indicator. Nike soared today. Just exploded straight up, like 9% right out the gate, and kept pretty much all of it. Nike is in the DJIA, so sent that up in an outsized fashion - tho' to be fair, most Dow components were up today, just not like that.
And I suspect a lot of the reasons the Dow components were generally higher is because the market is shaky, market sentiment is irrationally terrible, and the biotech sector midday - see that slide down? That's the biotech sector. Some of that money would've flown to (perceived) quality - like the Dow 30.
And biotech is represented more heavily on the NASDAQ than anywhere else.
So there's your explanation. Dow oversampling, NASDAQ oversampling, and the S&P500 in the middle.