Because J.R.R Tolkien only imagined the story, and because it wasn't revelation, he had to keep it to himself!
You really want to make a big deal about whether someone keeps something to themselves or they spread it around as some sort of key difference between imagination, fantasy, and revelation?
Revelation comes from outside the individual. And historically has spread quite rapidly from that individual. Why do you think this is? Mass delusion?
Maybe by definition "Revelation comes from outside the individual", but by definition invisible pink unicorns are pink. Claiming revelation comes from outside the individual doesn't make actual revelation exist. Reality is not obligated to provide us with real incidents of all of the imagined phenomena we can define.
It takes no more than misplaced trust and a desire to believe, not mass delusion, for something one person imagines (or lies about) to be spread around as fact. Fox News works like that. The reason bullshit can spread is the same in both cases -- it spreads because the target audience wants to believe what is being said is true.
As for making anything out of the speed at which information spreads, to quote Churchill, "A lie gets halfway around the world before the truth has a chance to get its pants on."
What you call an appeal to authority is instead a recounting of religious experiences. They have no inherent authority to appeal to.
When one person takes someone else's "recounting" as real information about an external influence like a god, and doesn't take it as merely the other's vivid imagination, that person is treating the other as an authoritative source of information. In fact, I can't think of a more pure form of appeal to authority -- the supposed authority doesn't need to document a reproducible methodology, doesn't need to provide references, doesn't need to provide credentials, etc.
As to appeal to consequences, well that's just silly.
When you earlier said "And the basic message is not bad. Quite the contrary." that hinted at the idea that people should be more generous in their criticism of religion because a supposedly good message comes along for the ride. I'd call that an appeal to consequences, if I read the intent correctly. It's a minor point I'm willing to conceded if I missed the mark.
Which brings us back to the starting point. Your measure of God is the scientific method.
Very well. Design the experiment.
Which brings you back to trying to foist the burden of proof on others to whom it does not belong.
Besides, I take that challenge, though not formed as a question, in much the same way I would take a rhetorical question. You only offer the challenge because you've ruled experiment impossible. You would only counter each offered experiment with reasons why that experiment was inadequate or misdirected. You expect others to treat it as a crowning feature, not a flaw, not a reason for doubt, that God and other religious concepts are founded on vague, fluid definitions and slippery accountability.