There's a pretty great movie about this story; https://en.m.wikipedia.org/wiki/Brotherhood_of_the_Wolf
Is it possible it was just an escaped lion? Has a lion ever lived in the wild in France?
The article mentions that under hypotheses. Not sure if sibling comment is being tongue in cheek but the article mentions menageries specifically
Maybe some wigbrained aristocrat got one for his menagerie. Alternatively: