Except we absolutely do have sensible hypotheses, that were ignored by that paper. And the mechanism is not a “virus did it”, so I’m glad you are not sold on that.
To be clear, these are not total explanations. God might still have intervened here, and perhaps his intervention was necessary. Science does not deal in absolutes, and it does not traffic in God’s action. It is just silent on these things. I am very happy to disclaim its findings with that. God’s help might have been needed.
We do have sensible hypothesis for how Octopi evolved. We do not know all the details, and we certainly haven’t ruled God out. Neither have we demonstrated that God’s intervention was necessary either.