Re: "if their strategy had been different in the 80's"
If they had patented and fought to keep what they invented, then the existing market would have worked around them and maybe we'd have a more diverse hardware and OS market.
Indeed. In the early years of the IBM PC, there were a lot of 8- and 16-bit systems available, and some 32-bit ones (like the Fortune 16/32). IBM's marketing power and existing customer base, plus the market for PC clones,1 led to the eventual dominance of the IBM PC.2 But it could have gone much differently.
Even after the IBM PC had caught on, there were certainly moments when it looked like there might be serious competition. Pretty much everything else outperformed it in one way or another. Had Apple come out with a Mac II-style separate-display Mac sooner, or released a cheaper Lisa after the Mac rather than before it... who knows? A cheaper, more open DEC Rainbow might have had a chance. Xerox might not have screwed up marketing the Alto so very, very badly. And so on.
1It's important to remember that the IBM PC was not the only architecture that got cloned. Apple had Franklin, for example; it was Apple v. Franklin that led to the use of clean-room development for cloning the IBM PC BIOS. (And that's apropos this article, since it was a software copyright decision.) And there were open architectures such as S-100, which started as the Altair bus but was widely used by other manufacturers.
2Lynn Wheeler has argued (in alt.folklore.computers, I think, and no, I'm not going to search for a citation) that the PC's ability to serve as a 3270 terminal - first through third-party cards like the DCA IRMA, then with IBM's hybrid 3270 PC, and eventually with 3270 and TN3270 emulators over LAN connections - gave it a big boost for business adoption. Mid-level managers could justify getting a PC to replace their dedicated 3270 terminal as a way to be "more productive", and it became a status symbol. Having made inroads with the 3270 users, it would have become a standard piece of business equipment at the managerial level; that reduced demand for the typing pool, which gradually disappeared, making PCs necessary for all employees who created documents. I don't know of any methodologically-sound research supporting this, but it fits my anecdotal experience of the era.