The Dash News is old stuff already known for a few days so why should it do anything to the market today
It takes time for news to spread and people to react.
For example, I'm online all day every day doing basically nothing but reading crypto-related news in-between my usual day-job activities, on all sorts of sites and from many diverse sources, yet even I -- totally plugged in -- only heard this Dash-exploit news just this morning (from the link here in this thread, as I said).
My reaction was to dump my coins immediately, and yes maybe I'm in the minority doing that (? or maybe not) and maybe "late to react" but multiply this anecdotal evidence example by a few tens of thousands of other instances over yesterday, today, tomorrow, next week etc... and there you go.
Good move IMHO. Many of us here (in the *toxic* Monero community) have been dubious of Dash's security because of the multiple attack vectors all it's many 'features' present. Dash is not quite the Rube Goldberg machine Etherium is, but they both suffer from this problem. That and the fact so much of Dash's feature set has had little peer review and scrutiny.