I am honestly not informed enough to say whether the whole Ghibli trend grew organically, or whether it came from OAI marketing.
And yeah, Myasaki can be a bit of a dick, but I don't think he's wrong here. I worked with both LLM and image generation for some personal projects, and you have to coax it a lot to get anything halfway usable, and even then, it isn't great. Even stuff that's heralded as exemplary by the corps behind the trend mostly seems kinda shitty.
Also, even if you like GenAI, most of the stuff that OAI is doing right now feels like desperate attempts to keep the hype train rolling, to justify their frankly ludicrous valuation.
As I said, two things can be true. He's a dick, but I still think he's right about this.