Re: Apple lucked out
If we think of what a tablet really does, and how it does it, from input to form, Apple pretty much did invent the tablet with the Newton. The ipad is the only other real tablet, certainly the only other one that meant anything. I know that some insist in calling the convertibles of the 2000's, "tablets", but they really weren't. At best, they could be called tablet-like, but just in a very limited way. The Grid, for example, never went anywhere, though part of that was Microsoft insisting that they would have a similar product that never arrived, giving the name to products that were never intended to arrive; vaporware. Yes, that was the origin of the word.
Apple may not invent some early version of something, but makes it useful in a way the original inventor didn't figure out. You mention PARC, and that's a good example. Apple may not have invented the GUI, as Xerox did. But Xerox's version was unusable. Apple invented the drop down menu, the overlapping windows and many more innovations. Xerox's own computer, the Star workstation based on their GUI, failed. That led Xerox out of computing. The failed Lisa led Apple to the Mac.