If you are looking for more specific details, I can provide: from Mojo Jojo's monologues.
: Through a flashback, we learn that Jojo was actually the one who pushed the Professor, causing him to accidentally spill Chemical X into the concoction of sugar, spice, and everything nice. While this created the Powerpuff Girls, the resulting explosion also mutated Jojo’s brain, turning him into the super-intelligent Mojo Jojo. [S1E7] Major Competition/Mr. Mojo's Rising
: The Girls become frustrated and feel obsolete as the citizens of Townsville quickly abandon them for the shiny new celebrity. However, they soon realize that Major Glory is more of a showman than a selfless protector. If you are looking for more specific details,
Information on how this origin story differs from the . : The Girls become frustrated and feel obsolete
In this segment, the Powerpuff Girls face a new kind of threat: a rival superhero who is more interested in fame than actually helping people.
: Armed with new powers granted by the Professor, Mojo Jojo attacks the Girls. However, the Professor realizes Mojo’s true nature and helps the Girls defeat him. The episode ends with the irony that Mojo Jojo is responsible for his own greatest enemies. Thematic Highlights
: Mojo Jojo tricks the Professor into helping him "improve" himself, claiming he wants to be a hero. He manipulates the Professor's guilt by revealing a secret from the past: before the Girls were created, Mojo was the Professor’s lab assistant, a simple monkey named Jojo .