First, RaTG13 is not an ancestor, it's a sibling. Next, the evidence is based on ratio of amino acid changes to silent changes, not based on similarity.
I think accidental release of a naturally evolved virus is still a plausible hypothesis. To discount it as "conspiracy theory" seems to be wishful thinking.
I will continue to monitor findings on this until more conclusive, non-RaTG13 derived evidence is available.