It’s not that deep. They got the rug pulled from under them when the studio slashed the budget. Instead of doing an ending they wanted, lots of action, with bad animation, they instead rebelled with a rewrite ending that used intentional vagueness and ambivalent philosophical storytelling that let them use their resources to focus on art design and keep the cool factor up. Tons of stills, but really pretty. That’s why a lot of the last sequences are just artsy backgrounds with only voice overs, there are several seconds of just white paper, etc. This however proved widely popular and the writing was vague but interesting enough to fuel hundreds of hours of video analysis and thousands of words essays.

The other factor was the mythological treatment of biblical imagery, which was rather new and unique at the time.