DL has not operated ATL-DXB on a daily basis in the winter for a couple of years.
It is certain that the growth of EK in the US is cutting into what DL carried since ATL-DXB like most of DL's ATL int'l flights is heavily dependent on connecting traffic.
DL also said it would reduce int'l capacity during the winter and this is simply part of it. AA also has released a number of int'l reductions some of which are deeper than in the past.
Americans do very little leisure travel in the winter; US int'l travel is more dependent on US originating travel than in the past due to the strong dollar. Given that predictions of a weakening of the dollar relative to global currencies and an increase in the price of oil continue to be pushed back further into the future, US carrier int'l networks will shrink in the winter when the cost of travel to the US is higher due to weaker foreign currencies. The converse is that US carrier int'l networks will be much more internationally focused in the summer and US carriers will push their networks harder at the times when Americans travel.
but it also highlights that there is slack in DL's international fleet which allows int'l aircraft to be used on the domestic system in the winter as well as for charter work. Many professional sports charters prefer using int'l aircraft because of the premium cabin seats; DL will carry a significant number of NFL teams.
Given that DL sees these market trends that are developing and adapts to them and finds ways to succeed in them, all stakeholders still win.