By "Smallville's" sixth season, the show had outgrown its original network, the WB. The CW was created from the merger of The WB and UPN, so the last half of "Smallville" aired there. Then, after the seventh season, Rosenbaum, Kreuk, and series creators Alfred Gough and Miles Millar left the series. (For the past three seasons, previous writing teams Todd Slavkin and Darren Swimmer, followed by Kelly Souders and Brian Petersen, were promoted to showrunners.)

In the 2021 oral history of Smallville on The Hollywood Reporterall four said they felt it was time to move on. Gough said:

“(Millar and I) did seven seasons of the show. They (the network) wanted to continue indefinitely. We knew it was going to go beyond season 8. We told the stories we wanted to tell. The show will go on. We coached all the people who were there and continued to run it “Okay, we think the best thing for us and for the show is to step aside and let somebody else do it. "

Rosenbaum said, “I didn't leave the show. I had a six-year contract and finished with seven years. And so I felt like I had done enough, and (Lex's) character had done enough." Kreuk also added that she started "Smallville" when she was 18, and when she left, she was 26. “('Smallville') was my entire young adult life. I didn't know what Lana's stories would be in the future I didn't want to live in a love triangle, I hate playing love triangles and I just wanted to explore other aspects of my life.

For their part, Gough and Millar conceded they probably dragged out the Clarke/Lana storyline too longwhich in itself could be a symptom of the show running longer than they expected. On an episode of Rosenbaum's Inside Of You Podcast with Goff and Millar, all three reiterated that by the seventh season of "Smallville" they were burned out. Then, at the beginning of Smallville's 10th season, the entire original cast besides Tom Welling himself having left. (Allison Mack, who played Clark's friend/Lois' cousin Chloe Sullivan, remained in a reduced recurring role throughout the final season.)

Despite the departure of Gough and Millar, the "Finale" ended the show as they had planned. In a 2011 interview with Collider A few months before Smallville ended, Millar said, “The last moment of the show will be (Clark) putting on the (Superman) suit and flying into his future and his destiny. It was always in our minds. be the ultimate end of the show."

That's right, the Finale ends with Clark ripping off his shirt, Christopher Reeve-style, to reveal a Superman suit underneath, then flying off to help people in need.