So 4 million G Suite business customers and 70 million educational G Suite customers is outside the core business? I would say 74 million customers is a major part of any business.
They do not have 74 million paying customers. However, I agree that the "free" version is safe for as long as the enterprise offering continues to do well (5 million PAYING users as of Feb 2019: https://cloud.google.com/blog/products/g-suite/5-million-and...).