From various statistics regarding Citizendium activity, it appears that some sea change occurred approximately in the 2006-2013 time frame that resulted in a marked change in the activity on Citizendium. This article presents some of this data. The answer as to what happened is unknown at this time. Coincidentally, some management changes occurred in this time frame, and in 2010 Larry Sanger stepped aside without naming a successor.
As the figures in this section indicate, the period of rapid growth for Citizendium never existed, with the number of new articles and of new accounts exhibiting a sudden U-turn in rate of growth. The number of new accounts approved shows an even more dramatic loss of interest. It is unclear just what happened in 2006-2013 to cause the slowdown in activity.
Numerous threads on Citizendium's forums have posed this question. See the article linked above and posts relating to this article here. The term 'editor' on Citizendium means a person who owns an article's content, which has nothing to do with the rest of this article.
In discussing the links above, the report suggests there may be a connection between the steady drop in the percentage of Citizens making at least one edit a year after joining, and the also steady drop in active editors that occurred in the same 2006-2013 time frame. One might conjecture this transition indicates no real change in climate at Citizendium. The graph shows that many new Citizens lost interest in continuing with Citizendium, the number maintaining interest dropping from over 750 to only 10. At the same time the number of editors actively contributing stopped rising and entered a steady decline to a level in 2012 of about 1% what it was at its peak in 2007. Discouragement of new contributors, whatever its cause, made it impossible for there to be any growth of Citizendium.
The history of the site shows an upsurge in the number of Constables during the 2006-2007 phase. The vast majority of today's Constables were added in 2006-2007: 4 of them active, and they serve as long as they wish with no effective means for removal, so they continue to put their stamp upon the project.
The transition of 2006-2013 is accompanied by a persistent drop in the number of new articles created, the times where something actually gets done, which have fallen to a very low number per year as reliance upon discussion of content has been replaced by simpler things such as constant bickering, or blocks by individual Constables on their own recognizance. On Wikipedia there is an average of 350 blocks per day, which hugely dwarfs the solitary formal case of 1 per month in arbitration. Sometimes, less bureaucracy is better. Who knew?