According to John Sorenson, if a Phoenician vessel was used, those aboard it quite surely would have been socially and culturally diverse. In the first place, those surrounding Mulek would have been from Zedekiah's court, the very crowd whom the Lord, speaking through Jeremiah, Ezekiel, and Lehi, frequently attacked as wayward, disobedient, and semipagan. Many of the elite of Jerusalem were worshippers of alien gods, as shown for example by the condemnation heaped on their heretical rites in Jeremiah 7 (compare 2 Kings 23). Likely no Levitical priests were among them, "and they had brought no records with them; and they denied the being of their Creator" (Omni 1:17). We can suppose that beliefs and ways of worship contrary to the words of the prophets and the law of Moses brought along by any sample of Judahites from Zedekiah's circle who managed to get away would contribute to their heretical condition. There could have been even more divergent practices among the crew of the vessel. [John Sorenson, "The Mulekites," F.A.R.M.S., p. 11]
Note* I would have to wonder, referring to the specific phrasing: "they denied the being of their Creator," if the people of Zarahemla, rather than being totally devoid of religion, were just specifically denying that Christ was the Creator. This idea was apparently one of the very things that they persecuted Lehi and Jeremiah in the Old World. [Alan C. Miner, Personal Notes] [See the Personal Notes after the commentary on Alma 13:16]