Obscurity is far more popular and widespread than popularity. Most, even we, the obscure, will, in a moment or more of popularity, never point this out and probably have a difficult time recalling its truth. But there it is.
To each an obscurity unto herself. Popular ideas can be uninteresting simply because their shared nature has shaved off all the interesting bits. Others are so interesting, and feel so profoundly connected to all of us, that we imagine they are hardly ideas at all, at least not those of individuals. What popular person could have invented forgiveness, passion, understanding? If these ideas came from us, maybe they came from many of us at once, maybe the seeds grew in all of us, maybe they regrow in each of us to this day. Maybe one of us had a bit of a notion, and shared it with a few more who worked and molded and shared with more, who rephrased and reshaped and inserted their own selves before passing it on yet again.
Plato may have described the jewel beneath the rough surface, whose nature we can infer, but I think our attempts to understand only make the idea rougher, exposing new crevices and tributaries, cracks and holes, outgrowths and sharp edges. The beauty is not buried deep within, and we are not digging. Instead each is piling on, adding ugly refinements to the whole.