^^ The adjacent article makes for an interesting read. I found this portion quite on point.
The letter writing campaign to keep Star Trek
on for a second season might have only been a nudge in helping to decide in favour of the show's return. Ratings wise the show was in that grey area, but it was reaching the audience NBC wanted to reach.
This kind of information should have been included in Cushman's book because it would have put his assertions in a proper context. Sure Star Trek
wasn't a runaway hit, but neither was it a disaster by any stretch. And it had things going in its favour such as reaching the desired demographic.
The audience at large---us---have long accepted that Star Trek's
ratings were bad and thus led to its ultimate cancellation. But in this context we can see that the ratings---while not stellar in terms of pure numbers---weren't anywhere near bad, and coupled with being strong with the target audience it justified keeping the show going.
Going further from the above goes to another point made earlier in the article: even a good performing show can be killed if someone doesn't like it for some reason or other just as a poor performing show can be propped up and kept going even if it's losing money simply because someone likes it.