nostr:npub1q9ma5xxhn8m69ztdj3lrefpnarszxgh3gk8wykkq53gfsl80mlssulzgdu By late-1960s standards, it was a low-viewership program. So it "failed." But somehow kept going.

Full disclosure: I grew up on re-runs of the original, still have my James Blish paperback adaptions, and a Star Trek Tech Manual with a James Doohan signature.