Helaman 6:34

And thus we see that the Nephites did begin to dwindle in unbelief, and grow in wickedness and abominations, while the Lamanites began to grow exceedingly in the knowledge of their God; yea, they did begin to keep his statutes and commandments, and to walk in truth and uprightness before him.

So we see that the Nephites began to stop believing. They grew in evil and terrible deeds. At the same time, the Lamanites began to know their God very well. They began to keep his rules and walk in truth before him.

So here’s what we see: the Nephites began losing their faith and growing in wickedness and evil, while the Lamanites grew strong in knowing God. They started keeping his laws and commands, living truthfully and with integrity before him.