The Atonement of Christ accomplished the building of Christ Church !
Matt 16:18
18 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.
Jesus here did not mean a literal church building, but His People, True believers in Him, upon the rock of He being the Christ, the Son of the Living God, and the shedding of His Blood..
Within this statement Jesus ensures there will believers in Himself, that is all that the Father hath given Him. His building His Church produces believers, Notice Jesus states " I will build my Church " take that freewillers, for Christ depends solely on His will and not yours to build His Church.
The word build is the greek word:
oikodomeō and means:
to build a house, erect a building
a) to build (up from the foundation)
b) to restore by building, to rebuild, repair2) metaph.
a) to found, establish
b) to promote growth in Christian wisdom, affection, grace, virtue, holiness, blessedness
c) to grow in wisdom and piety
This Ideal is conveyed in Acts 15 when James quotes scripture prophecy Acts 15:13-16
13 And after they had held their peace, James answered, saying, Men and brethren, hearken unto me:
14 Simeon hath declared how God at the first did visit the Gentiles, to take out[choose] of them a people for his name.
15 And to this agree the words of the prophets; as it is written,
16 After this I will return, and will build again the tabernacle of David, which is fallen down; and I will build again the ruins thereof, and I will set it up:
This also means that Christ Church was in the OT as well.
And Christ assures us that the gates of Hell shall not prevail against it !
The gates of hell cannot prevent one for whom Christ died from believing in Christ nor from going to heaven. If anyone of the church that the blood of Christ purchased as per Acts 20:28b
to feed the church of God, which he hath purchased with his own blood.
If anyone of them perish for their sins, then the gates of hell prevailed against the Church that Christ said He would build. If anyone of that Church dies in unbelief and perish in their sins as per Jn 8:24
24I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins.
Then the gates of hell prevailed against Christ building His Church.
If one goes to hell its because the gates of hell prevailed against them, that is the devil prevailed against them.
Unbelief is due to the devil blinding us 2 Cor 4:3
3 But if our gospel be hid, it is hid to them that are lost:
4In whom the god of this world hath blinded the minds of them which believe not,
Lk 8:12
12 Those by the way side are they that hear; then cometh the devil, and taketh away the word out of their hearts, lest they should believe and be saved.
So yes, unbelief is due to the devil being victorious ! He prevails preventing one to believe and be saved. Paul says this:
2 Thess 2:10
And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
Satan, the Devil, the gates of Hell is prevailing against such as these..
But Jesus Christ by His Atoning death will build a community of believers in Him, that shall follow Him..
He says as a complement to Matt 16:18 this Jn 12:32
32 And I, if I be lifted up from the earth, will draw all men unto me.
Thats His building, His drawing all to Him that He was lifted up for as the Son of the Living God.