The answer is simple.
Mormonism preys on Christianity. It is a parasite, following Christian missionary efforts to try to lure away the weak willed, the poorly grounded in Scripture, etc.
It doesn’t go and establish great works on its own accord. It is a cult. A heresy. An American false religion.
ampu
The basic premise of Mormonism is that the Church Christ founded somehow needed a restoration. Unfortunately, this cannot be true, unless Christ is a liar. The LDS claims that God chose Joseph Smith to reestablish the Church of Jesus Christ after it had disappeared some 1,700 years earlier following the death of the first apostles.
“And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.” Mat 6:18
Here Christ says his Church will not be destroyed.
“I have yet many things to say unto you, but ye cannot bear them now. Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.” John 16:12-13
“But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and foundation of the truth.” 1Tim 3:15
Here Christ says, and Paul reaffirms, that the Church will always teach the TRUTH.
Then Jesus came to them and said, "All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age." Mat 28:18-20
Again, here Jesus assures us that He is always with us, to the very end.
So Christ says His Church will not be destroyed or fall away from him, that the Holy Spirit will guide the Church to always teach the Truth, and He will always be with us.
The only reason for a ‘restoration’ is that Christ lied.
Luke 6:27,28
But I say unto you which hear, Love your enemies, do good to them which hate you, bless them that curse you, and pray for them which despitefully use you.
6:37 Judge not and ye shall not be judged: condem not, and ye shall not be condemned, forgive, and ye shall be forgiven.