They couldn't be bothered with doing that.
He knew that a graduate assistant had reported something to him. He took it seriously enough to report it to his direct superior and the de facto police commissioner with jurisdiction. He put McQueary in touch with them. This is not ignoring it and it is not sweeping it under the rug. Paterno was a 75 year old football coach, not a lawyer or a law enforcement officer. Make no mistake, there are a lot of guilty people in this case who could have and should have done more to stop Sandusky. Paterno isn’t one of them.