Not sure why Clines did it, but I'm pleased that he undertook the task of re-imagining the classic tale of Robinson Crusoe and adding a big dollop of H.P. Lovecraft to Defoe's original narrative. If you've ever read Defoe's version, you'll recall a number of themes including adventure, racial politics, religion, colonialism, free will and fate. Readers of the time would likely identify with many of his social positions and perhaps not even recognize the oft times disagreeable aspects of what Crusoe believes and does. Clines grapples with those themes and incorporates them into a more palatable mélange by changing the race of the island inhabitants/visitors into sub-human creatures, not necessarily of this Earth. Religions clash to a degree but this time, the aboriginal's gods are living, breathing monsters and not invisible entities as in the original version. The adventure story remains relatively intact (with clashes with the Lovecraftian gods being one exception) from Defoe's telling which still delights even modern readers.
It was fun to compare Cline's story to Defoe's to see where changes were made and the weird elements added. In some respects, this is a scholarly approach to make a classic a lot more fun to read. Please note, Clines maintains Defoe's story telling style that is a bit rough to plow through, but in the end, a good time.