Alma 30: 53 But behold, the devil hath deceived me; for he appeared unto me in the form of an angel, and said unto me: Go and reclaim this people, for they have all gone astray after an unknown God. And he said unto me: There is no God; yea, and he taught me that which I should say. And I have taught his words; and I taught them because they were pleasing unto the carnal mind; and I taught them, even until I had much success, insomuch that I verily believed that they were true; and for this cause I withstood the truth, even until I have brought this great curse upon me.
"Success" or having your teaching accepted doesn't always mean that what you are teaching is true. Nor does lack of success mean that what you are teaching is false.
Korihor says he taught the people, even until he had much success INSOMUCH, (meaning "to such a degree") that I verily believed that they were true. But it wasn't. He was deceived by the audience's acceptance of what he said.
Don't be fooled that large scale acceptance equals truth. The scripture more often than not show how a large scale audiences acceptance of a belief or message almost NEVER equates to the truthfulness of the message. Small audiences also do not mean it's false. The followers of Christ when he lived his mortal life were very small.