Ad 1. How about handball? Polish male team has some real successes recently and handball isn't as popular as volleyball.
Ad.2 Well, the demography can't guarantee great results. China, India, Pakistan and Indonesia have much more people than Finland, Serbia, Portugal, Holland, Czech Rep. etc. and I would say that they are rather much weaker at volleyball I think it is more about tradition, coaching system etc. not about amount of people. Or else Montenegro would never beat France. And such things happen.
and please, do not forget CUBA! I think they are like 11 millions!