Was giving Vatican City autonomy an attempt to preserve elements of Secularlism in the Italian government?
Not entirely, but definitely part of it. Here is a relevant quote from Wikipedia which may shed some light on the establishment of the Vatican as autonomous. In 1870, the Pope’s holdings were left in an uncertain situation when Rome itself was annexed by the Piedmontese after a nominal resistance by the papal forces. Between 1861 and 1929 the status of the pope was referred to as the “Roman Question”. They were undisturbed in their palace, and given certain recognitions by the Law of Guarantees, including the right to send and receive ambassadors. But they did not recognize the Italian king’s right to rule in Rome, and they refused to leave the Vatican compound until the dispute was resolved in 1929. Other states continued to maintain international recognition of the Holy See as a sovereign entity. In practice Italy made no attempt to interfere with the Holy See within the Vatican walls. However, they confiscated church property in many other places, including, perhaps most notably, th
