Wasn't Ford originally from Nebraska? That would explain why he did so much better there.
He was born there, yes.
Birth state means hardly anything in elections. Ford lost NE to Reagan in the primaries.
NE was also solidly Republican in '88 when most other plains were competitive due to the farm crisis. Also, Goldwater did much better there, winning two of the three CD's, than in Kansas, Oklahoma, or the Dakotas.
Maybe the Omaha area is a higher percent of Nebraska's population than other metros were of their states? At least KS has Lawrence, Topeka and Wichita, which I'm guessing all voted much more Democratic than the KS suburbs of Kansas City. Oklahoma has already been explained. No idea about the Dakotas, other than they haven't been anywhere near as partisan GOP as Nebraska in the last four decades.