Indeed, it’s said it wasn’t the campaign itself that saved Star Trek: it was the presence of Lucille Ball at Desilu Studios – which had produced The Cage and the TV series – who had personally intervened to save Star Trek. Such was NBC’s desire to do business with Ball.
So, yes, while NBC committed Star Trek to a third series, it did so on terms that ensured the program’s demise. NBC shunted Star Trek around the time slots, including 10-11pm Eastern on a Friday. Audience numbers inevitably fell off and that gave NBC the excuse it needed to set its phaser to the kill setting and fire.