Cardinal (Catholicism)
In accordance with tradition, they sign by placing the title "Cardinal" (abbreviated Card.) after their personal name and before their surname as, for instance, "John Card(inal) Doe" or, in Latin, "Ioannes Card(inalis) Cognomen". Some writers, such as James-Charles Noonan, hold that, in the case of cardinals, the form used for signatures should be used also when referring to them in English. Official sources such as the Archdiocese of Milwaukee and Catholic News Service say that the correct form for referring to a cardinal in English is normally as "Cardinal [First name] [Surname]". This is the rule given also in stylebooks not associated with the Catholic Church. This style is also generally followed on the websites of the Holy See and episcopal conferences. Oriental Patriarchs who are created Cardinals customarily use "Sanctae Ecclesiae Cardinalis" as their full title, probably because they do not belong to the Roman clergy.

Q: Why do Oriental Patriarchs sign this way?
because they do not belong to the Roman clergy