Xerox voluntarily gave up on the GUI. I know it seems hard to believe, but at that time they were simply into basic research. Computers were practically a hobby for them. They wanted to build copiers, not computers. Yes, Apple "made it happen" - just like Gates "made it happen" from his purchase of the original Windows source code while IBM got into the disaster that was OS/2. The similarities between the rise of MSFT and the rise of Apple are really astonishing when you look at them - both got their start because the real originators either decided to take a pass or just got off track somewhere along the line. To say that Apple has somehow succeeded at building on the original idea where Microsoft failed flies in the face of history. Both "built and built and built" on the original ideas.
I didn't mean to imply Microsoft failed to do it, only that Jobs saw it and first had the **gasp** vision (I hate that word), to do it, to put it in a tiny box. Oh, he also had Wozniak and Hertzberg and the rest of that crazy engineering team to make it happen. And if it weren't for that jackass Scully, the Macintosh was going to premiere at $1995.
Anyway, I only mean to say that in my observation, Windows GUI innovations trail Mac GUI innovations.
OTOH, Windows had true preemptive multitasking before the Mac...no small potatoes that.
To this day, that's gotta hurt. LOL