That that paper is one (very good) explanation for the early and sudden appearance of life on Earth, despite it being presumed a rare phenomenon. But there are

That that paper is one (very good) explanation for the early and sudden appearance of life on Earth, despite it being presumed a rare phenomenon. But there are other possible explanations. About the Great Filter, in principle we can expect the probability of those things to vary by several orders of magnitude, so only one would qualify. All of them being equally unlikely is actually harder to explain than the alternative.