Italy in 1913 was nominally an ally of Germany and Austria, but in truth more closely allied with France. It's possible that the French and Italian authorities wanted to avoid a public spectacle that would inflame nationalists in both countries and make it more difficult to keep Italy a defacto French ally.

It makes me feel uncomfortable that sentences for crimes are orders of magnitude different depending on where you are being tried.

I guess different communities have different weightings on certain crimes.