It didn't. That kind of thinking leads to all kinds of innovations in the name of righting the ship, and then before you know it they are so far unmoored from traditional Christianity that you end up with blatant frauds and heresies like Islam and Mormonism that deceive millions.
There is a difference between having problems (which all churches do) and actually becoming irrecoverably corrupt such that you have to be completely replaced by something else (Islam, Mormonism, etc.), which is the false restorationist narrative. Christ our God said that the gates of Hell would not prevail against His Church, and I for one do not believe for a second that He was lying or wasting His words.
Jesus wasn't lying, but a lot of folks have profited by deliberate obfuscation of His words.
There are two reasons why the church is now an ineffective failure. Today we see division heresy and licentiousness in the church. It's no longer a legitimate representative of the gospel of Jesus Christ. The current situation was predicted by its founder, Jesus Christ in Luke 21:24. The date for the beginning of its present decline was June 1967. When the IDF liberated Jerusalem, the times of the gentiles was fulfilled.
The primary causes of the decline of the church are two;
misinterpretation of scripture &
control issues.
Misinterpretation
Millions of Catholics assume that when Jesus said the gates of hell would not prevail HE was speaking about the Roman Catholic organization in general and Peter as first bishop of Rome.
If you parse the words of Matthew's gospel differently, you can apply it to the protestant communion. You'd make a huge mistake there too.
Scholars generally agree the passage in Matthew 16 applies to the general community of the faithful NOT to an ecclesiastical entity.
Unfortunately this is where everybody parts company with a logical interpretation of Matthew 16. If grace is grace, then grace would be grace for all. Unfortunately no one now believes such a thing to be true or even possible.
Instead we've got many denominations and separations of the church, beginning with The Great Schism of 1054 and extending into the Protestant Reformation to the present day. Each group claims to be THE ONLY vendor of divine grace, thus attempting to usurp the authority of Almighty God for its own benefit and profit.
You aren't going to please God unless you are a member of church X or synagogue Y or mosque Z.
Control Issues
The primary cause of divisions in the church (as well as Islam and Judaism) is control.
There can only be a small group of men in control of a religion at any given point in time. For those who covet power the only answer is to divide and create a new religion or a new perspective on an old religion. This is the primary reason for The Great Schism of 1054 as well as the Protestant Reformation.
The same thing happens in local churches with little or no governance of a denominational organization. I'm thinking of non-denominational churches at this point. Without denominational oversight or a heavy hand of management like that of St. Paul, divisions often result in congregational splits with no one in either group ever again speaking or having fellowship with anyone from the other group. One wonders how they will manage their affairs in heaven.
On a nationalistic level numerous arguments arise over petty issues sometimes resulting in outright war. The religious wars of Europe were based upon simple arguments such as the meaning of baptism, Holy Communion, grace, etc.
Control and misinterpretation issues arise simply because a man or group of men want to influence and control the spiritual lives of those who voluntarily devote themselves to their authority.
The baby Jesus is therefore left out in the cold because nobody is concerned about his well being. The crucified Christ is never taken down from the cross because if He ever came back to life His presence would threaten church leadership just as it threatened Jewish leaders who tried to kill Him in the first place. Jews deal with the cross by ignoring its implications and Muslims deny the whole episode altogether. Christians smugly sit back on their haunches, point their fingers at those who disagree and damn the whole lot.
There is little or no place for God or Jesus or the Holy Spirit in the modern church. Most members are too busy with their own affairs to bother seeking God's heart at any level other than a polite attendance once or twice a year in whatever church is open at a convenient time. According to PEW and Gallup polls, regular church attendance defined as one visit a month declined in 2010 to approximately 40% - 50% of 1950 levels. If present trends continue attendance will drop to 10% by 2050.
Questions about where the church went wrong are irrelevant. Nobody cares.
The one simple easy thing to remember is that these are the last days and it is time for all of us to repent and humbly seek God's mercy. He is still ready willing and able to receive all who come to Him in peace.
Will you?
that's me, hollering from the choir loft...