It's a spiritual battle 

Matthew 13:24-30

The Parable of the Weeds

24 "Jesus told them another parable: “The kingdom of heaven is like a man who sowed good seed in his field. 25 But while everyone was sleeping, his enemy came and sowed weeds among the wheat, and went away. 26 When the wheat sprouted and formed heads, then the weeds also appeared.

27 “The owner’s servants came to him and said, ‘Sir, didn’t you sow good seed in your field? Where then did the weeds come from?’

28 “‘An enemy did this,’ he replied.

“The servants asked him, ‘Do you want us to go and pull them up?’

29 “‘No,’ he answered, ‘because while you are pulling the weeds, you may uproot the wheat with them. 30 Let both grow together until the harvest. At that time I will tell the harvesters: First collect the weeds and tie them in bundles to be burned; then gather the wheat and bring it into my barn.’” "

The weeds in this parable is the apostasies and heresies being promoted in the Church by members of the Church's hierarchy.

Evil is allowed by God, it serves a purpose. It provides the opportunity for the people of faith to become even stronger, to become holy, and to bring others to convert, even maybe also the apostates themselves.

There is a tendency amongst the faithful today to believe that the Church has never been in such a dire state as it is now, with heretical teachings from the highest echelons within the hierarchy, betraying the Truth;Our Lord Jesus Christ.

But no, and this is reassuring, although it mightn't seem like it, the Church has always had this element within, it has served the others to grow in faith and to pass it on to the next generation.

And the Church will go on, because 

"In the beginning was the Word, and the Word was with God, and the Word was God. He was with God in the beginning. Through Him all things were made, and without Him nothing was made that has been made. In Him was life, and that life was the light of men. The Light shines in the darkness, and the darkness has not overcome it." John 1: 1-5

Those who believe in people, be it priests, bishops, cardinals, are putting their trust in men instead of believing and trusting only in Jesus Christ, are practicing  idolatry. 

As Saint John Chrysostom, Archbishop of Constantinople, considered as one of the Fathers of the Church, who lived in the 5th century, said:

“The road to Hell is paved with the bones of priests and monks, and the skulls of bishops are the lamp posts that light the path.”

But at the same time there remains many good faithful priests, holy priests, who still preach the gospel of truth, in this murky world infiltrated by lies and corruption.