The editors for the 1920 LDS edition shifted the word order here in Helaman 1:6 by placing the connective insomuch after the two conjoined prepositional phrases, “with his strength and also with his great wisdom”. English readers expect insomuch to be immediately followed by its that- clause, thus the motivation for moving insomuch in this instance: “insomuch that by sending him forth he should gain power over the Nephites”. Nonetheless, the Book of Mormon text often has examples of prepositional phrases that are displaced from their expected positions, as here in Helaman 1:16. For some other examples of displaced prepositional phrases, see under Mosiah 26:23.
In the original text, there are 176 occurrences of insomuch that. There is only one other case where insomuch is separated from its that-clause:
This example clearly shows that insomuch can occur considerably earlier than its associated that- clause. The text is firm for 3 Nephi 19:3: both the printer’s manuscript and the 1830 edition read “insomuch did they send forth unto the people that there were many …” (for this part of the text, both 𝓟 and the 1830 edition are firsthand copies of 𝓞). The inverted verb phrase in that sentence, “did they send forth”, also shows there must be some preceding adverbial or connective element (namely, insomuch). The meaning of insomuch in 3 Nephi 19:3 seems to be something like ‘so much’ or ‘so extensively’.
Summary: Restore the difficult but original word order in Helaman 1:16, where insomuch is separated from its that-clause by the displaced prepositional expression “with his strength and also with his great wisdom”; such usage can be found elsewhere in the Book of Mormon text.