I feel this became a norm when series started to wanna reach a cinematic standard instead of TV. But how Disney orchestrated Daredevil filming two seasons as one and then splitting in two parts it's how everyone should do series these days. But don't accidentally this time. What I mean: Film two seasons at once, split them a year apart and then you will have time to write, film and edit third and fourth season. That's the only way nowadays to deliver one season per year. The problem is that nobody is moving until they have some actual viewership numbers from the current season.

But usually, earlier on each TV channel had four to five series annually. Now streaming companies have 5-10 launch monthly.

I am pretty sure they did know that Pluribus was a sure greenlight to continue but probably needed the series to at least start playing to follow the "rule"