Welcome to the board, Bob.
We have one poster who's mentioned hitting it big through their website, and a couple more who've made their FIRE through Internet-related businesses. But I suspect that they're far less common than the media would have us believe.
Diehard business entrepreneurs also tend to never FIRE. They're having too much fun.
Golly, I'm new here myself, so I don't know about the "main philosophy," or even if there is one.
After you make your first 100 posts, Jeff, we'll e-mail you the secret codes for enriching yourself via day-trading the futures in an obscure commodity developed on this board called "beever cheeze". You'll be able to use the codes to unlock the additional features on your decoder ring, and they also include an updated video of the secret handshake.
It's hard to gather statistics from a group of DIYers who can't even agree on a common definition of net worth, let alone the most important factors in achieving FIRE, but a high savings rate is probably the most common one. That's usually a function of reducing expenses rather than boosting income. Entrepreneurship is also a big boost to FIRE (just like Stanley's "Millionaire Next Door") but not mandatory-- quite a few more of us wage slaves have FIREd by being driven to escape the clueless business managers.
So I tend to be a bit skeptical of books like the Four-hour Workweek that tell people what they want to hear, and we'll have to get back to that author in 5-10 years. But in the meantime, by comparison you're selling Brussels sprouts in the Dairy Queen parking lot...