What I found one of the key factor behind active communities particularly Tamil and Malayalam, is the support of Government for the initiative.  This could be a priority area for  other Wikipedias as well. 

According to my knowledge, World Classical Tamil Conference 2010 was the only time Tamil wikipedians and --cut--

More important is, to grow Indic wikipedias some community members need to take some extra effort.  

 But unfortunately, the community could not be strengthened due to various issues like access to Internet. computing platform, issues with rendering and input methods and we ended up with stub articles remaining in the same state.  

That is the case in all Indic wikis which used bots to increase the number of articles. According to me strength of the community also should grow as the number of articles grows. If we focus on community growth, articles numbers will grow as a natural outcome of that. As we already saw it will not happen the other way round for Indic wikipedias. As one editor pointed out in discussions, Users will be attached to a wiki only if they feel proud about it. So it is important that we should plan some programs to retain existing users and attract more new users to Indic wikis. We need to have some programs to bring back our old editors also.