Lol, why don’t you just read the Rails source directly?
I already don’t bother with tuts anymore and go straight to documentation. If docs are not sufficient and StackOverflow isn’t helping, I start source-diving.
The way to learn new domains as a developer is first to get a high level architectural view of the domain, set some kind of goal, then build it out using docs and source as a reference. The Rails Guides on the Ruby on Rails homepage are pretty good at giving a high-level overview of what’s going on.
Rails is crazy-complicated, but that’s only because the web is crazy-complicated, if you want a simpler framework, then I’d suggest Sinatra. It’s what I started with, the README gives you everything you need to get started.
Asking to understand everything is just asking for pain.