The GP is analyzing some dimensions to figure out if the success of Baldur's Gate is surprising or not. He/she finds that, given the limited dimensions we can consider, the success is surprising.
I read your reply as saying "no, it's not possible to analyze why games fails / succeed, because they're all different". I feel that's usually unhelpful: assuming we can't explain things because they're all idiosyncratic is usually not productive. It's more productive if you, for example, point to something extra that is missing.
I think OP is putting too much emphasis on brand and reputation. Blizzard had the best of both and they still manage to produce failure after failure (at least as far as critical acclaim goes). BattleBit had none is also a massive success. What makes a game fail or succeed? I don't think anyone knows. But I am fairly sure that whatever AAA mainstream is doing isn't really working. The biggest games are almost all either old franchises that usually have their roots in mods or some kind of simulator that just packages up and polishes something from the real world. So where has the innovation, the joy of video games gone? I think it's being smothered by spreashsheets and processes. If that's true then the solution is quite simple: Let people who actually like games and who can make games, make the games that people want.
I've not been in that industry but was for a while, the closest input metric I ever saw that correlated to success was how fast your tools let you iterate on ideas to find the core of what was "fun" and the polish it until it shined. Same applied to the art side of the pipeline, the more headache importing/iterating in-engine the more things diverged from render -> in-game.
Oh and how much publishers meddled in games and/or set constraints. At one point one of the big 3 wasn't approving games that didn't have multiplayer regardless of genre, got to spend ~5mo working on multiplayer that was totally broken until we got sign-off that we could pull it from the title.
I read your reply as saying "no, it's not possible to analyze why games fails / succeed, because they're all different". I feel that's usually unhelpful: assuming we can't explain things because they're all idiosyncratic is usually not productive. It's more productive if you, for example, point to something extra that is missing.