I would argue they aren't that separated. If the Mac hadn't got popular with the consumer market it could be said that Linux distro's could of been the popular choice for that market, as it's free and the Apple laptop ecosystem could of languished. The success on the consumer side fuels the viability of the laptop from the dev side as well.
If it never got popular on the consumer end and I couldn't manage my office docs and such on it, while I may use it at home, many workplaces and therefore the mainstream dev may of never adopted the Mac. What I use at "home", is what I want to use when I come into the workplace. There needs to be a critical mass before most workplaces (where many dev's work) to adopt it and therefore develop an ecosystem around it (e.g. your favourite IDE's, tool chains, etc)
I'm not sure about this. Dev's are by far not the mass market of the PC industry - definitely not enough to achieve large adoption. Office users, casual users, students, etc may not even know what a "Unix system" is. For them marketing, being in the "cool crowd", aesthetics, and broad easy compatibility IMO are the things that make them more comfortable making a purchase. Herd behavior is real, and the lines in front of stores, that everyone they know is talking about them, etc just enforce more purchases. It makes users more secure, and inclusive in their purchase of your device.
More just an anecdotal opinion but to me the iPad and iPhone (the ecosystem effect) and Apple's marketing are really what gave them the leg up on the personal computing level. I still remember those "I'm a PC, I'm a Mac" ads pitching the PC as the uncool choice. That's a powerful message to people and they must of thought it would work otherwise they wouldn't of run that ad - if not to dev's the general public. Individuals were buying them locally as home machines way before companies really allowed them for work because of this marketing and the easy integration to their other consumer devices - at least that's what I saw locally here (not US).
If it never got popular on the consumer end and I couldn't manage my office docs and such on it, while I may use it at home, many workplaces and therefore the mainstream dev may of never adopted the Mac. What I use at "home", is what I want to use when I come into the workplace. There needs to be a critical mass before most workplaces (where many dev's work) to adopt it and therefore develop an ecosystem around it (e.g. your favourite IDE's, tool chains, etc)