It's a long story, and it's also not complete yet (I'm actually doing very UI heavy work right now as a tech lead). It's also not really correct to say it started with UI - I was big into programming language theory in college, even implementing a bunch of toy interpreters/compilers, one of which even got some measure of fame on the Internet.
The 5 second overview is really that it's the same as getting good at any new skill. You find an area that you don't know how to do, and then keep working at it until you do know how to do it. Then repeat with finer-grained details. There were a bunch of skills involved in this project - C, HTML5, UTF-8 decoding, debugging, testing, autotools, CTypes, API design, documentation - that I wasn't all that good at when I started that I had to pick up along the way.
This is the most inspiring thing I've read in a long time. There's a lot of chatter on HN about how people became an "expert" in this or that, but for some reason, the way you phrased it really resonated with me. And to see the end result -- holy crap. HTML is complicated.
The 5 second overview is really that it's the same as getting good at any new skill. You find an area that you don't know how to do, and then keep working at it until you do know how to do it. Then repeat with finer-grained details. There were a bunch of skills involved in this project - C, HTML5, UTF-8 decoding, debugging, testing, autotools, CTypes, API design, documentation - that I wasn't all that good at when I started that I had to pick up along the way.