Helaman 4:13

and because of this their great wickedness, and their boastings in their own strength, they were left in their own strength; therefore they did not prosper, but were afflicted, and smitten, and driven before the Lamanites, until they had lost possession of almost all their lands.

Because of their great evil and bragging about their own strength, they were left to their own strength. So they did not do well. They suffered, were beaten, and were pushed back by the Lamanites. They lost almost all their lands.

Because of this wickedness and their arrogant confidence in their own strength, they were left to their own strength. So they didn’t thrive—instead they suffered defeats and were driven back by the Lamanites until they’d lost nearly all their land.