Because the rights-holders are the ones building the attraction! This whole thing exists because Media Invest Entertainment and its sister company Nikal want to exploit the rights. Or, at least, that's the excuse they've given Blackpool Council - as you say, the website is laughable but could easily dupe a stupid politician.Chariots of the Gods is about the idea of aliens having visited the Earth in the distant past. You don't need the rights to the book to build an attraction based around that particular concept. So if they've ditched the title, why pay anything in royalties to the rights-holders?
And remember, even though the whole complex has been renamed there will still be an attraction within it named Chariots of the Gods, along with that fake museum also based on Von Daniken's books.