In a strange way, being no longer used as a spoken language actually helped Hebrew. People were learning to speak a language that was not a low prestige language stomped upon by some dominant one, but instead a language with no status at all in spoken usage. In Palestine there also was no media or society at large to be competing with, especially for the youth out in the Kibbutzim, the farming communities set up by the socialist Russian immigrants of the second aliyah. There it was possible to get an entire community to start speaking Hebrew without external interference. Few if any modern language revivals are in this situation.
The revival of Hebrew was also helped by the massive numbers of young immigrants of the first and second alyot. They got behind the revival and were willing to work to build a Jewish language to go along with their independent Jewish nation and identity. In the case of national language revivals this drive is often much less powerful and widespread. These immigrants also were coming to a new place with the intention of radically changing their way of life, from urban to agrarian. Changing their language along with all the rest was not that much more. In the case of a population that just wants to revitalize their language, there's not the symbolic and irreversible immigration to select the truly committed and put them in a place together. Instead, some dedicated people who want to change the language are together with many people who are open to the idea but not committed and some who are stubborn, far less ideal conditions.
We come back then to the question of when it is practical to revive a language in a given domain. It looks like, from the experience of the revivers of Hebrew, that there are several factors needed: