So what happened and why a Mac Pro?
This is extremely simple to understand. Let's do a way-back machine.
It's 1985. THE MAC IS OUT! It's the computer for "the average guy" and IT'S THE FUTURE... OK, so what does it cost? $2000!??! That's half of a new car (Yugo). What does it do?? ... almost nothing. And you have to spend thousands more in software to do anything!!
Remember there was no proper internet, just a group of ASCII dial-ups. No video editing on these things yet, and if there, it was it was so clunky. No music organization. Aside from text and photo manipulation, word processing and spread sheets, the Mac was a toy. Most of what it did in 1985 was pathetic.
Imagine spending about $5000 these days on something that did almost nothing for an average consumer. Yeah. FAIL. It wasn't such a bad failure, because it was the idea of what technology would accommodate as a successful form over a decade later. The Mac line became famous for print production and photo manipulation through the late 80s and 90s; there was a palpable niche market, but it needed MORE power and MORE storage and MORE EVERYTHING. Smartly, Apple fed that market which supported their hardware sales.
The industry was going bonkers with towers. Design was horrible. Everything was a mess of incompatibility by the late-90s... with PCs. If you wanted to use a PC in the late 90s, you needed to spend weeks just studying how all the bits and pieces work or didn't work together. It was hell. Apple didn't have that problem, but they were following the trend of under-designed boxes until Jobs came back.
Jobs came back at the right time when hardware, software, and the internet, made computers able to be what he envisioned in the early 80s. The iMac started a downward-design revolution where things were compacted and limited to allow average people access to computing, and by the late-90s, computers could actually appeal and apply to an average person. The Pro was still necessary, since there was still a huge professional market that needed the power of the bigger processors and top hardware.
Today, 2011, the Thunderbolt connectors have made the Pro line close to useless. There are still, and always will be, professionals that need the fastest processing power available, but 99% don't need it for video editing or print production or website building or internet browsing, etc. You can use the smallest Mac and hook up personal storage needs. Only high-end gaming and CGI work and special-niche computing benefit from the Pro-form computers anymore.
What Jobs saw for the computer has now been enabled by the technology. What computers had to be between the genesis of the home computer and today was necessary to fuel an industry which progressed the technology along until computers were able to meet Jobs' vision.
2015: the MacPro will be an antiquated curiosity. Towers will be passe technology. Kids will laugh at what their parents used to get on the internet or organize music in 2005. iPads will be as fast and capable as a 2006 MacPro tower. Mechanical devices within computers will be almost history. Laptops will be rare, and they will look clumsy to the average person. Most all computers will be tablets.
Steve Jobs will be completely within his prime, his vision for the world of computers at a zenith of form and function. Unfortunately he is dead.