Former Seahawks defensive end Frank Clark
Frank Clark left Seattle because he wanted to get paid, and he did. In 2019, Seattle traded Clark to the Kansas City Chiefs after working out a deal where Clark would be franchise-tagged and then dealt. The Seahawks would have had to create cap space for Clark, but Seattle had the money to move around. Instead, Seattle to see the bottom dollar instead of the production and Clark left.
The season before Clark, he had 13 sacks and 27 quarterback hits which led Seattle. He also had 10 tackles for loss. His presence also made it easier for defensive tackle Jarran Reed to see more one-on-one blocking and Reed had 10 sacks and 24 quarterback hits. Clark was only 26 years old when he went to the Chiefs so he would have had a number of years to be a very good Seahawk.
After Clark left in 2019, Seattle's sack leader was Rasheem Green who only had 4. The leader among the defensive line in quarterback hits was Jadeveon Clowney with only 7. In 2020, the leader in sacks among defensive linemen was Reed with 6. Meanwhile. Clark made three straight Pro Bowls with the Chiefs and is closing in on the all-time postseason record for sacks.
Seattle still hasn't really resolved the loss of Clark. The team rebuilt its defensive line this offseason mostly because they couldn't stop the run, but to be fair they couldn't get sustained quarterback pressure either. Clark should have never left the Seahawks and his staying would have helped fix many of the problems that have arisen since he left.