Before the French knight of St John Jean Quentin d'Autun wrote his description of Malta in 1534-1536, Malta already had a strong tradition of St Paul's shipwreck on the island around 60 AD. This cult was very strongly reinforced by the Order of St John who were fighting the Moslem Ottoman Turks and the Barbary pirates during this period. Grand Master Alof de Wignacourt was inaugurated as Grandmaster on February 10, 1601, and this date was chosen for the celebration of the apostle Paul's shipwreck on Malta, then and ever since. Scholars in the know realise that the shipwreck actually occurred some time after the Jewish Fast, the Jewish Feast of Atonement known as Yom Kippur, occurring around the end of September, hence in late October or early to mid-November, the season when ships did not ply the Mediterranean because of the unsettled weather. Hence February for this shipwreck is a slightly modern symbolic invention.
That the apostle Paul was around November 60 AD indeed shipwrecked on Malta, known in antiquity as Melita Africana, is a near certainty. The late, lamented and learned Paul A. Guillaumier wrote exhaustively on this subject in The Sunday Times in recent years, and appears to have settled the argument in favour of Malta.
Please note, however, that on Gharbi island in the Kerkenna islands, east of Tunisia, the main town is Melita, and the island itself is also known as Melita. Moreover, the airport on Jerba island in south-eastern Tunisia is located at a place called Melita. Nevertheless, the latter appear to be weak points, and there has never been a claim for Tunisia's islands as the site of the shipwreck. Paul's third and Alexandrian ship, the Dioskouroi or Twin Brothers or Castor and Pollux, all terms representing the same classical gods, sailed directly for Sicily's then main city of Syracuse, hence our Malta as its departure point makes perfect sense. That Paul subsequently healed Publius's father and many Maltese islanders is reported in Acts 28, and can be relied upon.
That he preached to the islanders who worshipped the Punic gods, the Roman garrison who probably worshipped the Persian god Mithras, and the Roman administrators including Publius who worshipped the Roman gods and the emperor, is not reported, and is hence open to question.
Even more so is the theory of Maltese conversions to Christianity, in my view. Until the 4th century AD, Christian burials and tombs are missing in Malta and Gozo. We start meeting them especially after the reign of the emperor Theodosius and his enactments making Nicene Christianity the new state religion, which spread throughout the Roman empire, in the late 4th century, precisely from February 27, 380.
When in 869 and in 870 the Aghlabite Arabs invaded Malta and Gozo from the port of Sousse under Oqba bin Nafi (I have a Tunisian school textbook with a graphic map at hand), it is likely that these islands had been christianised under the Vandals, Visigoths and Byzantines. What happened with the Aghlabite invasion is not fully known for lack of written records, but many Maltese are reported to have fled to nearby Sicily and Italy, leaving a token population.
The islands were then islamised from the 11th century, around 1054 AD, until 1224, when under Swabian-Norman emperor Frederick II most Moslems who had not converted to Christianity were expelled to Lucera in south-eastern Italy, in order to pre-empt an uprising here and in Sicily.
When the Aragonese-Catalans took possession of Malta in 1283, re-christianisation could continue in a more pronounced manner. Religious orders started moving into the islands from Sicily: Augustinians, Franciscans, Carmelites, Dominicans and later the remaining orders, starting around 1372. In this sense, it is to some extent true that under the Aragonese and the Spaniards Malta was re-converted to Christianity.
The snake's argument has been covered by many previous correspondents, and it would be redundant to go into it here.