Jesus predicted churches will be corrupted, is he right ?
One has to look at history to see what happens. The very original Christians, right after the death of Jesus, were public enemy number one, subject to holocaust type persecution. If you did not renounce your faith, and lie about it, you were tortured and killed. This killed off most of the original faithful who would not compromise their faith. What was left after most of the original faithful were murdered, were Christians who were a little more secular watered down. Their survival required a more pragmatic world view, in line with secular bias. If you lied to appease the secular mob, you would be rewarded with your life. This was negative conditioning by the mob.
The original seven churches, during the first century, showed some of the effects of this secularism and regression. Philadelphia was the exception. Most of this had to do with secular compromises and integration; power and politics. As an example, in modern times, if secular/atheist culture wants abortion and your church forbids it, you become an outcast and a target of the angry mob. If you allow abortion, in your church, culture is more accepting, but you become labeled as corrupt in terms of Christianity by the same mob. It is no win, since you are dammed if you do, and dammed if you don't.
By the fourth century, Christianity becomes the official religion of Rome. Rome was not the official secular of Christianity, since Rome was a world super power. Rome was in charge and makes changes to suit the needs of the official religion of a world empire. This 4th century merger was a reward to the Christian soldiers, who were the most fearless in the Roman army. Rome was on the decline and these soldiers were the best fighters. With this merger, the word of God could be preached to the entire western world, without fear, due to Rome. The Roman Catholic Church is the descendent of ancient Rome.
Through the dark and middle ages Christianity is mixed with Roman imperialism, with that no nonsense Roman toughness. By the 15th century, the church begins to split; Protestant movement. This helped to separate and isolate Rome and Christianity. Now there are pure churches and churches much more secular in the spirit of Roman excess and perversion. This split is also why atheism (Rome) is also never too far from Christianity, in terms of hostile interaction. The persecution returns the more atheism separates from its roots in the merge.