Because think about it,
Toddlers are at the age where they put things in their mouth, If a toddler grabbed something dangerous and swallowed it, Who would we blame? The toddler or the Parent?
Mojo jojo was baby Chimpanzee, baby chimpanzees are known for their destructive nature. Professor Utonium being the freaking pet owner. Decides to leave a baby chimpanzee alone, in his house and in his labartory filled with chemicals and other dangerous devices.
Where he can either hurt himself or cause an accident, Which is very ironic because what happened next he did both.
When he got back from the store, He completely ignores mojo (A baby chimpanzee with a destructive nature) rampaging in his laboratory.
Until, he caused an accident by pushing the Professor into chemical X. and baby monkey JoJo, not knowing any better comes closer to the pot which caused an explosion. Which he ended hurting himself and causing an accident.
But, You know what? None of this would have never happened, If Professor Utonium was a better pet owner. Sooo, Technically, The powerpuff girls were created by
Sugar,
Spice,
Everything Nice
And Professor Utonium's negligence.
So, The person who actually made the PPG, is Professor Utonium
