Well… yes and no.
You kinda have to look at what’s profitable for different miners. Some do it for the long term and mine, in this case, Zcash regardless of the price.
Some do it for the short term, but you have to keep in mind that everything went down, not just Zcash. So while net $ profits went down, you don’t have anywhere else to point your miners at if you want to “make a quick buck”.
Hypothetically, if only Zcash dropped to 100$ and everything else stayed at their prices from lets say, a week ago, THEN you would have seen a much larger decline in difficulty.
Hope this helps, @Bakes
Alex