From the spoilers I read on that manga's final chapter, Axe-kun did us a huge favour with how much of a mess the story became from that point, and that's putting it kindly.
If my memory serves me right, the island and inland sea was mentioned to be filled with monsters in the WN/LN, so it wasn't as if there was a vibrant shipping economy in the area to start with.
Look, daddy of the year over there wasn't exactly big on the thinking before doing from chapter 1, MF just managed to avoid the consequences so far because of his (unconfirmed) wife and others.
Don't know know how true or exact numbers, but apparently the books didn't sell well in JP. That said, you'd got to wonder, is it actually bad bad or bad comparatively to bokuben.