I notice the absolute statement in the headline is qualified right away at the start of the article.
What if we are alone, at least as physical beings? What does this mean for people who believe that life spontaneously appeared and then evolved to where humanity is today? Their supposition about the origin of life itself implies that it must also have taken place elsewhere. Thus this quest to find other life is a quest for validation of their existential issue.
So, even as they vigorously deny that God exists, these people grasp at anything that can prove there is no Creator or Master Designer in the universe. These people will join their peers and colleges in the grave. See Psalm 49.
Bingo.
I'm as curious as the next person about the answer, but at this point my suspicion is that Fermi was right.