Kerry was just a horrible candidate.
Don't expect the same thing in 2008, though!! Expect a much more competitive state.
Kerry was an ok candidate. Not great, for sure, but he did almost defeat a sitting president in the middle of a war, albeit a minor one. The counties that Mondale and Dukakis won were in Litte Dixie, which like Dixie as a whole has continued to swing hard to the GOP. Many of the old hardcore FDR folks that still voted Dem in the 80s are now dead. Oklahoma will not be even remotely competitive in 2008, primarily because its two urban counties, Oklahoma and Tulsa, are Republican strongholds.
Kerry was a terrible candidate. It was only a month after the election that polls began showing a majority of Americans thought the war was a mistake. There was no reason for him to lose and no reason for him not take a single county in Oklahoma.