I started by checking the ownership of the videos on YouTube (through Content ID). All recent videos are claimed by emails on a domain entonegroup.com. The domain itself yields nothing as it's registered with an extra privacy option.
However the email leads to a lady that works for Entertainment One that also advertises [0] the ownership of the content.
I also checked the earliest videos of Peppa and it seems like they were produced by a different individuals, which would suggest that, at least this show, was acquired by Entertainment One.
Because as far as I can gather using Wikipedia, Entertainment One is the company behind the _real_ Peppa Pig. If you're saying that there is also reason to believe that they are behind the _fake_ Peppa Pig, that would be much larger news, which (looking at the amount of interest in the story), it isn't.
Edit: Ah, mFixman suggests a plausible explanation:
> Entertainment One owns Peppa Pig[1]. It's likely that Content ID thinks Elsagate is legitimate Peppa videos.
> [1] https://en.wikipedia.org/wiki/Entertainment_One
That makes more sense :)
But from the home page you're redirected to an URL without the trailing slash that doesn't work when copied and pasted.