Don't forget that Jobs picked Cook.
But when Jobs picked Sculley, he was young and inexperienced. He probably had never worked with 'an MBA' so he didn't know what to watch for
Also, the relationship with Sculley went downside fast. When things don't match, this is usually what happens.
For Jobs, a private or merely theoretical manifesto wouldn't have been enough. Apple designs everything from the concept to the manufacturing process to the unboxing and initial startup experience. For a something to be a true design reference, it had to cover all these bases. That means it needed to be a real product that actually shipped. Which it did.
If you measure the return using everything that followed its lead - which includes the flagship store - it has recovered its investment a bazillion times over. Whatever else the Cube may have been, it was not a mistake. The one-button hockey puck mouse with the too-short cable? That was a mistake.
Another way of looking at the Cube (and its successors) is that it's a `desktop laptop'.
Now, identify one - just one - computer that shared those trademark corners when the Cube came out. Nothing else looked even remotely like it, including Apple's earlier products. Now, there's little - if anything - done by Apple that doesn't mesh with the Cube beautifully. Even the individual keys on the current wireless keyboard (which I'm using to type this) and the trackpad off to the side are clearly post-Cube, and entierly consistant with the direction it set...a decade ago.
In terms of towering achievements in industrial design, the Cube is to computing what the 1927 Yankees are to baseball.