1. That the controversy over switching from Lisp to Python was a "turning point" for Reddit's traffic. Such a minor controversy wouldn't have generated sustained traffic. And indeed when you look at Reddit's lifetime traffic graph, there aren't any visible inflection points; it is overall a pretty smooth upward curve.
2. The reason Digg got more traffic was not some subtle difference in SEO strategies, but simply that (1) they started several months earlier, and (2) they promoted the site energetically to their enormous core audience of 15 year old gamers.
3. The reason it seems from talking to the Reddit founders that "success was not so difficult" is that Steve and Alexis are such understated guys. Simple design always looks like it was easy. Actually they worked quite hard.