Hahahaha it's not a matter of how great Wordpress is. It's a matter of when you submitted it, the fact that it had domain age so it had already been around, and then if you had ANY links pointing at the site already and how many you made. And then all that was coincidently done right before or around the time that an updated crawl was sent out, meaning you just caught it at the right time. There's nothing you can do to recommend or say to ensure that others would have the same story.
Quality content and many backlinks, not to mention many many ping actions result in very fast indexing - using google's properties such as YouTube also builds upon this and increases the speed of indexing
That's not exactly true. Just because you use wordpress, doesn't mean you'll get indexed faster than sites that don't use wordpress. Using a certain CMS has NOTHING to do with how fast you get indexed.
Yes, mostly new web sites are easy index from Google, at specially wordpress theme blogs. and if we have quality of content then also easy index site.