It just doesn't add up

(as the irritating professor says in the Citroen commercial)

D.M.Loades' "Two Tudor Conspiracies" claims that the French didn't back Thomas Stafford because they already had Mary of Scotland up their sleeves - indeed Hicks cites Loades as a source which is why I borrowed the book.
However, why supplant one Catholic Queen Mary with another when TS is not merely a Protestant but a Continental one at that?!