This, I guess, leads me to another question...who was it that took over the Trek reins when Roddenberry died? Was it some Paramount appointee who had no affinity for Trek and therefore had no need for Arnold? Or was it someone already involved in Trek who just didn't like Arnold? I'm a little fuzzy on the whole list of succession and how we got from there to here *. I mean, I know some of the names like Berman, Braga, Piller, Moore, stuff like that, but I don't really know who ran the shows and made decisions in the franchise, "official" titles aside.
Think of it like this. The series' producers were the final authority. Paramount Licensing was the intermediary between the producers and Pocket Books/DC Comics/etc. If the producers don't like something or don't approve of it, Licensing tells the licensee that it's no good and needs to be changed.
Richard Arnold came in between the series' producers (specifically, Gene Roddenberry) and Paramount Licensing.
The contention of the authors during that time was that Arnold was approving (or not) the manuscripts on the producers' end. The contention of Arnold is that Roddenberry was doing the actual vetting on the producers' end and he was just there as a stenographer or somesuch.
After Roddenberry's death, Arnold had no role in the process. And in the producers' chair, nothing really changed. Rick Berman had been with the series since its beginnings (actually, even before Roddenberry, as Berman was a part of Greg Strangis' Star Trek
project), and Roddenberry, as he fell ill (around the third season), became a figurehead insofar as the television series was concerned.
That may be why Roddenberry and Arnold were injected much more closely into the comics and novels; that was an area where Roddenberry could still exert influence.