As you encroached on ye’s territory, it did so on both fronts, being used for the plural and formal singular. The informal singular was still thou, in those centuries in which English maintained the informal/formal pronoun distintion that many modern European languages still have: tu-vous, du-Sie, tú-usted, etc. But gradually social change sealed you’s triumph. Using a plural to address a single person was once reserved for the very highborn, but made its way down the social ladder until any social superior was to be addressed with you. It didn’t stop there, though, as vous and Sie did. Instead, having once crowded out ye, you now edged out thou in the early modern period.