Because it’s the same with every large organization that has existed for a long period of time, legitimately every single one. What happened in the church was pure evil and the people who were complicit were, are and should be punished and prosecuted. The fact of the matter is the church hurts less kids than the police you would call or the social worker who covered the case, or even the parents of the children.
You could say the same about schools. There have been many cases of abuse by teachers. The issue is the individuals, not the church. People in the church do not condone that behavior, but in many areas of life there will be sick individuals contracting the goodness that is supposed to occur.
Any organization made up of a large number of humans will have evil people within its ranks. There are 1.1 billion Catholics, thus there will be a large number of bad people. And there will a large number of good people too. The problem comes from misrepresenting, both intentionally and unintentionally, the magnitude of the scandals and the role that the Church played.