So I don't know if there's some math behind it to explain this or if it's some kind of bug, but I just had everything in my city only needing 1 turn of production, from districts, units, projects (yes even space projects), and every single wonder. Here's an image of my production page. My production in my capital doesn't warrant every single thing being 1 turn of production. This lasted for around 5-10 turns, I forget the exact number.

Here's how I think it happened, but it still doesn't make a lot of sense to me: So I got the Great Scientist that gives you 100% Space Project production and the Great Scientist that gives flat production (around 1000-2000) for Space Projects in one turn, and I used both in my capital at the same time that was producing one of the space project components. I also don't know if getting 2 Great Scientists is possible in 1 turn, I was spamming Campus Research Grants but I'm not sure if that would give me 2 Great Scientists at the same time. Anyways, after that turn, everything in my capital went down to 1 turn of production. I was able to get Ruhr Valley in 1 turn when the last time I remember checking it was around 10-14 turns in my capital. I also finished the last space project in 1 turn right after. My guess is that the flat production carried over to everything else, but it specifically says the production is only for space projects.

Any thoughts? I was playing on Deity, Quick Speed.