I had no idea, but listen to this:

To novice Beatles fans, I warn you not to believe the hype about “Revolution 9.” I’ve listened to it many times over the years, waiting for the light in my head to switch on so I could unlock its mysteries. All I’ve ever gotten out of it is the vague feeling that immediately after listening to it, something is going to rise out from under my bed and butcher me in my sleep.

That’s, uh, JBev at JamsBio Magazine. The magazine did a big list of 185 Beatles songs, starting with the ones the magazine disapproves of and working up toward its very favorite (“A Day in the Life”).  Good idea, it’ll give people something to link to.
I like “Revolution No. 9,” though it’s not the first song I’d listen to. I go for tunes, especially bouncy tunes. Anyway, I pretty much played the Beatles to death when I was a kid. Back then received opinion held that “Revolution No. 9” was gibberish. But it isn’t. It’s a sound collage, of all things, and it holds together.
Decades later I check in again and find that “Revolution No. 9” has become a sacred cow. When did that happen? I’m guessing 1995.