It's obvious. The Nikon F5 (1996) uses the push-button/dial user interface, particularly "press mode button, rotate dial to change mode". This kind of interface, on a professional camera, appeared first in the Canon EOS 1 of 1989.
Manufacturers are influentied by others, what's the outrage about that?
BTW Nikon, during the 50s to early 80s, was usually a traditional, conservative company, not a highly innovative company. Pentax released a SLR (and SLR lenses) much earlier than Nikon. Pentax also released an electronic AE SLR before Nikon. Everybody "copied" Olympus after the release of the OM-1, the market went to more compact cameras and lenses (IMO, for worse). Nikon "copied" Minolta when making their first fully-featured AF system for the F-501 and F4 cameras.