Well, there are people who need two card slots, like wedding photographers. They may also need some video capability as well. And if they're Nikon shooters they'll definitely have the Nikon glass they need for their job. They won't want to purchase lots of Z lenses given they've got their F lenses. Low light capabilities will be excellent, and over 2200 shots with a fully charged battery isn't bad at all.
Actually, I think there are a lot of people who'll get this camera. Sure, it's not a camera for wildlife shooters. But then not everybody shoots wildlife.
Hermann
Hermann - I think you nailed it. The D780 is a very nice update in a lot of areas for a D750 wedding, event or portrait photographer. They don't need the resolution of the D850, they need two cameras and dual cards, and the D780 provides almost everything you have in a Z6 except the EVF and mirrorless.
The other way to look at it is it's a much better regular resolution camera to pair with a D850. I felt the D750 was underwhelming compared to a D850. It was more than just lower resolution for events, weddings, etc. The D780 is a legitimate second camera.
So here is the list of upgrades and updates:
Newer sensor
Faster focus
New EXPEED processor
Faster shutter
Better weather sealing frame
Better video
Dual Faster SD card slots with UHS-II instead of UHI-I
175% Longer battery life / 2200+ images on a charge per CIPA std.
Updated control layout to better match D850
5fps shooting with a full buffer compared to 2.5 fps using a D750
This D780 camera is an updated little brother to the D850. It's $1000 cheaper than the D850/Z7 price point - much better aligned as a modern all purpose camera. It's a big step up from the D750.