First, yes, I do buy that if top officials discovered it this morning, interviewed players and guilty staff, and got a confession, then they would take immediate action. It is an obvious honor code violation and even PR officials will tell you to get out ahead of the publicity. I would expect a private religious school to be less bureaucratic and more decisive about this than a public school.
Second, who's "they"? Since some in the athletic department were in on it, obviously some officials at Notre Dame have known about it for a while. Equally like some other Notre Dame officials found out about it today. Were there officials who looked the other way and tried to be ignorant? That's for an investigation to find out.
Why do you buy that? Organizations that have rules or bylaws have a procedure in place. That procedure takes a lot longer than a day to complete.
According to Notre Dame's honor code guidelines:
1. A faculty member that believes a violation occurred must have a meeting with the student
2. If the faculty member believes a violation occurred after the meeting, he must fill out a written report
3. If a student admits to violations, it must be stated in the report and a provost must review the admission, the report and also any agreed upon penalty between the student and faculty member and decide if the agreed upon punishment is just
4. A student, even if he admitted to violations, can revoke such admission within seven calendar days of the report being submitted and a hearing between a "honesty committee" will be scheduled
So you're telling me that you buy a written report was submitted with four players all confessing and agreeing on a punishment, then Notre Dame learning of and accepting these findings all in one day?
I have a bridge to sell you if you believe that.
http://honorcode.nd.edu/assets/63629/student_guide_to_the_academic_code_of_honor_web_aug_2011.pdf
These processes take time. They are not wrapped up in one day. It's convenient they learned of this and it leaks out on a Friday afternoon. That's PR work.