Why not get a Z6 or D850 instead? You can get a used D850 for that price. And it's got the same sensor as the Z6 but 500 euro higher price and the Z6 allows you to use all its functions with the EVF, such as eye autofocus. Is this product targeting videographers?
The D780 has the optical viewfinder which many enjoy, and now for the first time in Nikon DSLR, features a more generally useful LV AF with OSPDAF, which should be nice for low and high shots (e.g. crowd view from above) even with the subjects moving. Also it autofocuses screwdriver AF Nikkors which the Z6 does not. The price is higher than the current price for the Z6 but will no doubt be reduced once it has been available for a while and the initial surge has gone.
I don't think Nikon targets videographers who only do video, but photographers who also do some video, but a lot of people now are finding themselves in situations where video is expected.
The D850 autofocus during video ... well, it's best used to prefocus before the video recording starts. It's not really something you want to use during the recording. OSPDAF should change that. Hopefully Nikon launch a standard zoom with AF-P to complement the 70-300 AF-P to further improve video AF. The D850 does have focus peaking but it's not available during 4K recording; I would expect this to work in the D780 even in 4K recording.
Personally what I'm interested in is better LVAF, not so much video.
