That model no longer works in the modern age. Simply put, there is demand for viewing coverage of the olympics that is not being met, thus they are leaving money on the table. Unfortunately for them and for their potential customers they are constraining themselves to a business model that is obsolete. They are doing the equivalent of covering the olympics via newspaper in a television era.

They need to provide live streaming coverage of a wide variety of events, whether for free (with ads) or for a fee. That's the minimum bar these days, if they can't meet that bar people will just get their olympics coverage some other way (such as pirated bbc coverage) and NBC will still have lost out on a massive amount of potential revenue. And in the meantime they will have tarnished their brand as well.