I was very surprised by this as well. From the article: "The person familiar with OpenAI’s departure said the company’s rent had not been covered by a typical lease, but rather a less formal agreement paid for by Musk, the billionaire who also controls automaker Tesla and social media firm X."
Surprising OpenAI and Microsoft were OK with this after a $13B investment.
Musk is offering it for sublease. That means Musk is still paying the rent, just that he would let it out to someone else rather then occupy it himself.