S2 was announced before S1 aired, but S3 wasn’t announced until S2 finished. Ditto S4, which was announced as the final season in the summer of 2007, after S3 aired, but before the Writer’s Strike (which is proooobably what led to the year hiatus during the mid-season finale of S4).

I’m not going to say that it wrecked the plot. BSG certainly wasn’t as zany as Lost (which jumped the shark because ABC wanted to turn Lost into a Greys Anatomy 20 season bonanza and refused to actually allow them an end-date. The writers DID know where they wanted to end up going, but the goal kept getting pushed back - see Billiam’s 28.4 hour 5-part deept dive into Lost

Anyway TLDR; if you want to mysterybox TV, you gotta know what you want from the start, and you need to make sure the executives give you the number of seasons to get there in the end, which is a problem because capitalism hates art, etc and so on.

IMHO BSG fell into the same “Mystery Box Storytelling” pit that Lost did at around the same timeframe. Set up a mystery, and hope you can come up with a satisfying resolution by the time it matters. The trouble is that’s NEVER been how satisfying mysteries work. Seat-of-your-pants storytelling has its place, but not in a mystery. @Jennkryst is exactly right about how that wrecked the plot. They painted themselves into such a corner that the only way out was divine intervention.

BUT I still love the show. Low-tech sci-fi military stuff is my jam. The characters are great. The writing in any individual episode is usually stellar, especially in the early seasons.

They didn’t have a plan. “They” being the writers. The Director admitted as much in one of the Director commentaries for the first season in the DVD set, and the moment I heard it I lost all interest in the series. Babylon 5 had established how one pulls off a well-planned sci-fi series a decade prior, and that numbskull thought he knew better.

B5 is always, always, always my comparison point for shows that just completely shit the bed on pulling together the mystery that they’ve been dragging out for however many seasons. It got messy towards the end because they were cancelled and then uncancelled, so rushed through the ending of all the main arcs in Season 4 and then built Season 5 largely out of things that were supposed to be hinted at… but that was network fuckery. Not the writers. Otherwise, it would’ve been about as close to perfect as a show with '90s costuming and the same repeating shots CGI visuals can possibly be.

And writing a show with central mystery works the same way as designing a game with a central mystery. You don’t have to know all the details right away. They can stretch and grow and shift with time. But you absolutely have to know the answers to the Big Question going in. It makes everything else consistent and solves plot problems more often than you’d think when you can go, “Does this contradict the Big Answer? If it breaks the Big Answer, it doesn’t belong in our story.”

Spoiler

Buuuuut… according to the Plan (movie), the Cylon Plan (plot device) was different from Head-Six’s ‘God has a plan for you, Gaius’ (quote that Tricia Helfer really hates, thankyouverymuch). Then again, it’s easier to go back and try to slot in ‘oh we had a secret plan all along, this is what it was, and also it ended by Episode (whatever)’ after the fact.

Anyway, I also endorse BSG Reactica for watching, it’s gotten me to go back and re-watch the episodes for a fresh reminder again.