Nihilism merely means that life has no purpose. This can be sad if you need external purpose to give you direction, but it also creates a vacuum for internal purpose to give life purpose and take direction. Nihilism can lead to happiness if you're an internalist who interprets it positively. Externalists will struggle with this though. At best, they become chaotic and burn out after failing to organize their own lives because they parasite off the meaning of others.
I think Nihilism is generally considered as a form of depression, where an individual regards life as "meaningless", however I don't think this is the case. I am quite nihilistic and find that life can be just as happy as anyone else's. The whole point to Nihilism is that life doesn't inherently have any purpose, except to simply exist. This isn't necessarily depressing, only if the individual sees it this way. I find it quite liberating, because I believe that our lives are completely dependent on us in terms of happiness, and that I don't have to worry about failing because failure is only something that we humans created for ourselves, and not that it exists independently in the outside world. So I think that Nihilism can even lead to a happy life.
As Wikipedia says:
Most commonly, nihilism is presented in the form of existential nihilism, which argues that life is without objective meaning, purpose, or intrinsic value.
Oh, it's so close... Life IS without objective meaning or purpose; but it IS NOT WITHOUT INTRINSIC VALUE. You cannot be happy until you embrace the intrinsic value of life!
If people aren't motivated to advance society, or morally inclined to treat others the way they would be treated, then more likely they will struggle to make ends meet and not have a lot of friends, but enemies. However, they themselves may be happy because none of that will really matter. But then, what does?