Both Nikon and Canon waited too long to bring out their FX/FF mirrorless cameras.
They let Sony get too far ahead.
And when they had to make the switch, it was the entire landscape, cameras and lenses.
I remember the early Sony days when people were complaining about the lack of Sony lenses.
The situation has flipped. It is now Nikon and Canon with a lack of native mirrorless lenses.
Nikon HAD TO make the FTZ to bridge the lens gap while they came out with more Z lenses. Canon did same with their EF to R adapter.
Yeah, a big issue with Nikon is the mechanical AF lenses. The FTZ does not support them, so if you have many of them, you are stuck. You either keep going with the dSLRs so you can use the lenses, or go mirrorless and replace the lenses.