However, you can not argue with the fact that ATL has far more connections than JFK. CID, FWA, and SBN might only combine to contribute a few people per week to the new service, but there are so many cities like them that have ATL service and nothing to JFK. It all adds up...
That fact quickly becomes irrelevant when you apply filters like
1) Where are the Indian population centers
2) How many of those already served by SkyTeam thru their own European hubs.
3) Who else is serving those markets thru one-stops
The way I see XNA and TPA are likely candidates left out. That means this route's viability hinges on 45 true O&D passengers.
In a capacity controlled market like the US, carrying a transit passenger with two huge bags at a discount just to feed your discounted/competitive. Delta can make more money feeding others non-stop.
Both US and India are large countries with high fragmentation, there are 40 US cities with 10K or more Indian population probably from 15 Indian cities.
Indians don't like 2 stops. All US-India non-stops end up being two stops for most, even if 9W has 31 connections at BOM.
US feeders operate very old Barbie/Jungle jets, Indian side you get a relatively new A320/737.
Delta's problem is sparse coverage in India, one non-stop from one place is not going to attract passengers.