Why was the project not supported by those who needed it
- People now a days do not care about personal development, unfortunately they care about quick financial gains. I am sure If you could introduce any idea for them to make money then they would happily join there. (i.e: awarding referral bonus, revShare for being active etc etc)
and what can I do to improve the project?
Think about a marketing angle where people will find they will have a financial gain (a greedy way). Believe it or not this is the best bait. Even the biggest food chain Mcdonald's use this bait. A cheese burger for £0.99 but you actually end up spending £5 to £10. It's marketing strategy mate. Give people that they want.
If there is little interest, should I just leave it to fade away?
Depends on how big your cause is. If it's very BIG then stick to it. 1 year/2 years/5 years/10 years... Be consistent. Someday you will figure out how it should be worked.
PS: I noticed FitToTalk since you launched it but did not find it interesting because there were not many members to hangout but I am changing my mind. I am going to join now to support the cause (assuming the cause is big for you)