I think you will find that the D750 was more of a direct competitor to the 5d3, it was introduced at the then "street price" of the 5d3 had 6.5 fps and the 51 af points that was from supposedly the d800 et al. Nikon users on forums had been clamouring for a more direct replacement to the d700 than the d800 was (too many pixels - too large a file size). Like the D750 the 5d3 was untill recently listed as an enthusiast camera on some of their websites.
as for the claims about sales, the "gargantuan" bit refered to the PR disaster that was the D600 and not sales which I did describe as huge. The D600 had an embargo put on it in China, was replaced by the D610 within a year and Nikon had to offer replacement cameras to people who bought the 600. That is a worst case scenario for any company so describing that as Gargantuan is not hyperbole.
I never once said that the nikon cameras were not superior to Canon- in fact I do agree that there are many superior points in their favor. The Sensor is in the D850 and also the d810 and 800 obviously had more resolution and dynamic range, than any Canon. However the file sizes are huge. The d850 is approx 100mb files compared to approx 40 in the 5D4, not only does this create great pictures but it also requires more storage space and faster computers to post process at a reasonable speed. As for dynamic range, well I am not a landscape shooter, I have never hit the DR limit of my DR limited camera. I am sure there are many instances where almost 15 stops of DR at ISO 64 are useful but how many times do you really need that much without having a completely black photo? for myself I prefer higher ISO shooting, in which case both systems are much closer.
The Frame rate on the 850 seems fantastic, espescially when you include the stated buffer. However some reviewers (Matt Granger on youtube for one) are disputing the buffer claims. The AF module on the 850 seems to blow even the 1dx2 away, never mind the 5d4, untill you get into the small print. 153 af point of which 99 are cross type, sound great untill you see only 55 af points can be selected by the camera user and of those only 35 are X type. the Canon has 61 AF points of which 41 are X type all can be user selected, sounds like a draw to me. one place the Nikon did do a really good job is putting the XQD card in one slot, Canon should have used C-fast in the 5D4 but obviously felt that it wasn't needed. Also Nikon does have one feature in the metering which is better as it can be linked to the AF point whereas Canon is more center focused. I really think that while the headline features are good on a closer comparison there isn't that much of a difference- at least to draw Canon users of FF cameras.
You said using sales figures as an arguement was a mark of desperation I am pretty sure however that Nikon themselves will be more concerned about the sales figure and Market share than any customer will be. Nikons own main focus IS and ALWAYS WILL BE profit, that is the #1 priority, #2 is market share. Unfortunatly for Nikon their market share has slipped to the new entrant in the market which is Sony, Canon's has also lost market share but Nikon seems to be feeling it more. only in the last couple of weeks they announced a factory closure of a camera producing factory. There is a limited pool of people that will buy a $3000 camera, most people will be happy with their smartphone. To Gain Market share Nikon has to Target the Canon customers as Sony is producing smaller lighter cameras with about the same DR as Nikon. As A canon shooter myself, I really did look at the D850 but I just cant find a really solid reason on comparison to what I already have. This is why Sales and market share is pertinent to this conversation.