Well, arguably there was no established customer base for WPEngine before the launch. You either were a hobbyist and hosted for free on wordpress.com. Or you were a multi-billion dollar enterprise and used Automattic's premium hosting service (serious $$$).

OK. Thinking about it, there might have been a market there all along, but how come no one served it before? I mean Jason is crazy brilliant (talk to him, it's an experience!), but surely others could have come up with the same idea - right? I guess we'll never know, but my guess is that not too many people went out and searched for a thing like WPEngine before WPEngine