Ah, I'm always suspicious when I see blogs claiming about "real story behind X", this one not being an exception. I was wondering why I had trouble finding sources that didn't point to a conspiracy theory or a fan fiction about it.
Take for example this story about her origins dating back to the times of Pre-World War, written on a fandom wiki:
Not to be confused with The History of Peppa Pig. In 1912, famous comic artist at the time, Aurèle Charlot Poulin (1872-1960), had ended his comic strip Little Cats (1894-1912) and ended his contract with Bande Dessinée Drôle, and wanted a new idea. Poulin was raised on a farm with many cats and...
peppafanon.fandom.com
You'll notice that it's much more elaborate, with dates and events (despite some inconsistencies like somebody wanting to make "an anime cartoon series as no studio had been doing that before", and then proceeding to run it; the word "anime" wasn't even a thing back in the 1910s). However, if one is careful enough, they'd see in the home page that the content available there is fan-made.
Meanwhile, The Guardian, a British daily newspaper, gives me a completely different story from the 2000s through the word of Peppa's producers themselves:
‘After its success, we’d go to meetings with lots of ideas for other shows – but they just wanted 3,000 more episodes of Peppa Pig’
www.theguardian.com
So there's stories everywhere on the Internet about everything. Personally, I'd rather trust The Guardian in this case