There's certainly ample amounts of reasonable doubt
Innocent until proven guilty. Proven guilty beyond reasonable doubt.
But neither am I convinced of his innocence.
Fortunately, in most cases, we don't have to prove someone is innocent as that is very difficult in most cases. While I can prove my innocence in the JFK murder, I cannot prove my innocence in the murder of Halton McCollin (who was murdered very close to where I was at the time).
If there is reasonable doubt whether an arson occurred, there is even more doubt that he is guilty of arson.