“And notwithstanding the signs and the wonders which were wrought among the people of the Lord, and the many miracles which they did, Satan did get great hold upon the hearts of the people upon all the face of the land.”
I don’t think this is just talking about the non-believers turning further away from the Lord. It says “people upon all the face of the land”. This is a warning to the believers in Jesus Christ that even we can be led away. We need to be humble, prayerful and believe the scriptures; the Bible and the Book of Mormon.