Here in the printer’s manuscript, Oliver Cowdery initially wrote “the indifference concerning the freedom of their country”; but then virtually immediately he corrected the the to their by crossing out the the and writing their supralinearly. The original manuscript is not extant for the determiner here, but spacing between extant fragments favors the longer their. Moreover, their works better. Quite possibly, the following the in “the freedom” may have led Oliver to mistakenly write “the indifference” initially in 𝓟. For a list of other cases where Oliver miswrote their as the, see under Alma 27:23.
Summary: Accept Oliver Cowdery’s immediate correction in 𝓟 (giving “because of their indifference concerning the freedom of their country”), also the most likely reading in 𝓞.