Here in the printer’s manuscript, Oliver Cowdery initially wrote because without the preceding yea; then almost immediately he inserted the yea supralinearly (and without any change in the level of ink flow). The construction yea because occurs five other times in the text, as in this nearby passage:
There is nothing unusual about Oliver Cowdery’s correction to yea because in Helaman 9:24. Either reading, with or without the yea, is possible. Thus the original manuscript, which is not extant here, probably had the yea.
Summary: Maintain in Helaman 9:24 the instance of yea because, the corrected reading in 𝓟 (the earliest extant source).