Harry and Megan

[Lods]

Who is lighting it and what fuel are they using though?

I don't see where the issue is. Is it simply royalists dirty on them leaving?

Books and interviews are what's got the current blaze going.
Papers love it  so they'll have a hundred different logs to throw on it.
(the latest one I just read is that Harry took so many psychedelic drugs they've caused him to open up too much). :
Royalists are dirty on them, they think a lot of it is made up or exaggerated.
Anti-Royalists love them and see it as the beginning of the end for the monarchy.
Many folks who watched the interviews have taken them on board without questioning them, often because of a personal bias....some have genuinely been swayed to sympathy by the interviews and to some extent changed their minds.

My personal point of view is that there is probably elements of truth in what Harry is saying, but I also believe that folks on the other end would have a completely different perspective in telling their story.