I'll blame the Ottawa Renegades. In 2001 we had the second most regular season wins in the league. The expansion draft seemed to hit us harder than most, while at the same time our owners decided to save money by not re-signing key free agents. The slide in performance was noticeable in 2002, and we've never quite recovered.
The jump the shark moment may have been when Hitchcock lost a step. While he was in his prime, receivers and backs ran away from him or paid a heavy price. His play anchored the secondary and, some might argue, the whole defence. I miss the days when he used to fly to the sideline and kill a receiver or run up and destroy some runner. Then he slowed and was moved to LB and the Cats haven't been the same since.