It started on 4Chan and then moved to 8Chan. It is pretty much impossible to know if it was the same person on each site.

Both are correct

It started on 4chan as a troll. It was a meme at the time to have these "government whistleblowers" post on 4chan with anti-Hillary stuff. There were a bunch of them, like FBIAnon and CIAanon. Where they failed, and the four kids behind Qanon succeeded, is that they were too specific with their predictions that never happened, while Qanon was vague and cryptic, so it had lasting power. The account changed hands several times before being taken by Jim Watkins who later owned 8chan.