The original text here had the subordinate conjunction that after “it came to pass”, but Joseph Smith deleted it in his editing for the 1837 edition. Interestingly, the 1892 RLDS edition supplied the that, probably unintentionally. The RLDS text has continued with the that, even though Joseph crossed it out in 𝓟 and normally the 1908 RLDS edition follows the reading in 𝓟 (including the corrections that Joseph marked in the manuscript). The critical text will, of course, restore the original that, following the earliest text for each case of “it came to pass (that)”.
Most instances of “it came to pass” in the text are followed by that, but not all. But when “it came to pass” is followed by the prepositional phrase “in that (same) year”, the original text always has an intervening that; and in one case (marked below with an asterisk) there is a repeated that after the prepositional phrase:
Only here in Mormon 2:1 has the intervening that been removed.
Summary: Restore the subordinate conjunction that after “it came to pass” in Mormon 2:1 and wherever else the earliest textual sources support the that in that position.