Did Stephen Hawking prove the multiverse? That is what many media outlets have asked when introducing "A Smooth Exit From Eternal Inflation?" Hawking's final paper before he passed away on March 14, 2018.
His last 16-page work of quantum mechanics has been touted as something that either proves or disproves the existence of the multiverse, but it’s not as definitive as many news outlets would have you think. While “A Smooth Exit…” certainly discusses the multiverse, it’s purely from a theoretical standpoint.
The paper is more about creating a working model of a mathematical equation to measure the other universes hypothetically formed after the Big Bang. Rather than being a defining statement, Hawking’s final work is more of a question being posed to the scientific community.
So no, Hawking did not prove the multiverse, but that was never his intention in the first place. Instead, he was trying to help build a new model for the evaluation of those things which we cannot - and likely will not - ever be able to see.