It seems like Ron had some scenes and moments and a vibe that existed concretely in his head for the third game, and beyond that not much else other than the confidence that chasing those ideas would result in a good game. My guess is that’s how he started on the previous two and it’d worked out well. Not everyone works by plotting out all the details of their world in advance, and basically no one works by figuring out a bunch of symbolism and “what it all means” before putting pen to paper* - interpreting a work is usually a fan or critic’s job - so it seems very likely that nobody knew the answers to these things until the next game was made.
*I’m aware that people like Tolkien and Lucas seem to work this way, and their process is legendary among nerds like us, so people who are into nerdy things think that their worldbuilding-and-symbolism-first approach is a normal way to tell a story, but at least historically it’s actually highly irregular!