Geography makes Sardinia close to everyone that Lawrence mentions: It lies 120 miles (200 km) west of the mainland of Italy and 7.5 miles (12 km) south of the neighbouring French island of Corsica, and 120 miles (200 km) north of the coast of Africa. Its capital is Cagliari and the island itself is about 9,301 square miles (24,090 square km) with a population of about 1.5 million.
The name Sardinia, is a corruption of Sargon II the Assyrian King who became a god in 721 BC who completed the defeat of the Kingdom of Israel capturing Samaria after a 3 year long siege and exiling the inhabitants. This became the the basis for the first major Jewish disapora and the legends of the Lost Ten tribes, all of which is mentioned in Isaiah xx:1.
In the year that Tartan came unto Ashdod, when Sargon the king of Assyria sent him, and he fought against Ashdod and took it; 2 At that time Jehovah spake by Isaiah the son of Amoz, saying, Go, and loose the sackcloth from off thy loins, and put thy shoe from off thy foot. And he did so, walking naked and barefoot.
3And Jehovah said, Like as my servant Isaiah hath walked naked and barefoot three years for a sign and a wonder concerning Egypt and concerning Ethiopia; 4so shall the king of Assyria lead away the captives of Egypt, and the exiles of Ethiopia, young and old, naked and barefoot, and with buttocks uncovered, to the shame of Egypt. 5And they shall be dismayed and confounded, because of Ethiopia their expectation, and of Egypt their glory. 6And the inhabitant of this coast-land shall say in that day, Behold, such is our expectation, whither we fled for help to be delivered from the king of Assyria: and we, how shall we escape?
In Roman times though , Sardinia was a prison island, where the Roman Republic send their political (namely Christian) refugees. It’s harsh environment punctuated by still active volcanic action, and prone to earthquakes, made it mineral rich, but foreboding.
Little proselytizing occur except among the fellow convicts and a few early saints cropped up like Hippolytus, & Pope Pontianus both who exiled there. The earliest martyr being Saint Saturno died there in about 303 AD during the regime of Diocletian. Paul himself never went to Sardinia but he received visitors from there.