As you beat up this dude, do you ever like, stop to think about his backstory and whatnot. Like, even just listening to the bossfight theme, you can almost hear his growing insanity. He's not only been sleeping for what was it, 12,000 years (I think), but when he came home, he had nothing. Everything he had been taken away from him. So I think he attempts to cover the world with fuzzy ooze with good intentions; after all it worked with tthe octarians so why wouldn't it turn inklings/octolings to mammals too?