The article nicely points out that the decline of Volapük is connected to reform attempts that originated from within. It also mentions that Esperanto had similar issues and some people went ahead to create a derivative language Ido. What it doesn't mention is that why Esperanto continued evolving while Volapük fell apart. One reason usually attributed to its longevity is that Zamenhof, creator of Esperanto, became aware of human tendency to "improve" or reform constructed languages and saw it's been happening to Volapük. So he simply added into the Esperanto manifesto that the rules of Esperanto are "untouchable". So, he stated, that if you attempt to change parts of the language, you cannot call it Esperanto any longer, in an attempt to prevent diversion from the common roots of it.