Life arising only once could very well be the more plausible option
Indeed I feel like coming to this conclusion is something that the authors - and most of us rationalist types - do not _want_ to come to.
Because if you accept that hypothesis, then it follows as a consequence that an alternative view of the world makes a lot more sense: what if, rather than living in an emergent, random universe where life sprouts up everywhere, hundreds of billions of times, but somehow _always_ disappears before we can ever observe it outside Earth, we are instead living at the center of a universe where we are the sole intelligent species that ever existed? In that system of the world, the universe is being directed by beings existing outside its bounds - gods. A simulation created and managed by uncaring observers - as hypothesized by the likes of Elon Musk? Or a benevolent God in the Judeo/Christiano/Islamic tradition?
The truth is that this alternative is being rejected a priori, indeed not even acknowledged, by the authors of the article or most people in this thread, because it is an affront to their core beliefs, not through pure logical reasoning.