Blood, if you watch episode one again, you realize that's the last episode... I just watched it yesterday and I was like wow...
Idk if they meant to delay the explanation till last episode or to tell us that it's a cycle of time, because in the episodes later he went back in time and spilled his blood on Kurisu, which is what he saw in the first episode, and that triggered everything.
It's an awesome anime idk why you didn't like it that much o:
I prefer this type of anime that makes sense in the real world, too much fiction makes me feel like a kid. lol
If you know more animes like this tell me please

About that vid...
Yea, that's one special episode. If you enjoyed the anime you'll enjoy it too. Idk if it's worth watching for you, but it was for me.

Oh btw, there's a new movie of Steins;gate. It will be released somewhere in Jan, I think 30th.