There's only been one movie with Kang ("Ant-Man 3") and the reason it underperformed is because well....it's the 3rd Ant-Man movie.
The next appearance of the character was "Loki" season 2 which was a hit. So I'm kinda confused by what you mean.
Fred.
The MCU is in a phase that culminates with 2 Avengers movies in which Kang is the main villain. They’ve been setting it up since Shang Chi with the bands that allow people to teleport and summon things from other dimensions to Loki season 1 where they showed the sacred timeline. It’s all setting up the Kang saga, but people have lost interest. Their movies are making less money, not more. People have lost interest in the shows too.
For Disney, Streaming Losses and TV’s Decline Are a One-Two Punch (Published 2023)
The company experienced a sharp decline in its traditional TV business for the second straight quarter and will raise subscription prices for its streaming services.
www.nytimes.com