"MS originally got into small businesses because they had the home PC market sewn up. They leveraged that to get into small businesses, then rode those small businesses growth into supporting large businesses. "
No, that is not how it happened.
Microsoft got into corporations due to signing a deal with IBM to provide the DOS and other software for the IBM PC. Small computers were not taken seriously by large businesses until IBM got involved.
The "home PC market" at the time was all hobbyists. People with Radio Shack TRS-80s, Apple 2s and Commodore PETs. All of these had some version of Microsoft BASIC. But that is a far cry from "having the home PC market sewn up". They were not even called PCs until IBM came along. They were called "home computers".
Also, none of the above were business machines. None were made by a long term business products company. The IBM PC was a business machine, for obvious reasons.
There were a many "business computers" from several companies at the time. All were running CP/M (DOS) from Digital Research. The problem with these computers is that they did not share a common disk format, nor graphics format. The IBM PC changed all of that, by standardizing everything.
Had Gary Kildall (the head of Digital Research) reached an agreement with IBM, CP/M would have become the dominant business computer DOS instead of MS-DOS. Had that happened, Microsoft might have been a distant memory by now and this place might be called GSX central. GSX being the Graphics System Extension to CP/M. Windows was originally the Graphics "extension" to MS-DOS.
@naddy69 , most of your facts are correct, including CPM, but that largely predated PC's, didn't ever really compete with them (Digital Research lost the contract with IBM over legal concerns with the contract, so IBM went to MS who was hungrier and accepted it, then DR tried to compete with MS with DR DOS vs MS DOS, and I preferred DR DOS for a few features it had back then, but MS made sure it had compatibility problems from old MS' "destroy the competition and salt their land" business strategy model of the 1990s), but you then reach the wrong conclusions on the market development.
IBM PC's were not used by large corporations in the early days of the PC. They were used at home (I'm including PC and PC Jr), in schools, at home businesses, and at small businesses. Large businesses used mainframes and minicomputers. PC's were not considered serious enough or useful for enterprise use. And while much cheaper than a minicomputer, it was far more expensive for what they could do to put one every desk than something like a DEC mini with hundreds or thousands of dumb terminals, so not cost effective either. Different systems had different OS's, but if you had to pick a primary enterprise OS, it would have been a form of UNIX. MS had virtually zero footprint in that space even after they had already become a household name.
Microsoft dominated the small business market, beating TRS-80s and Apple ///'s (Apple's early attempt at a business computer, which flopped), but only became enterprise focused as those small companies grew and took their MS "infrastructure" (if you could call it that) with them.
Even after Windows 3 came out and the PC and Windows had already become dominant in the lower end market, Tandy having long since bailed and Apple falling to a niche among designers with the Mac and the negligible share for everything else that it's only slowly clawing upward from today, PC's and MS still had almost no presence among high end microcomputers. That space was also controlled by various UNIX systems, including Solaris on Sun's SPARC workstations, SGI (Silicon Graphics), and others running on various RISC chips. Windows NT was their answer to this, with early versions running on both Intel and RISC processors. That was really the turning point for them, and Moore's Law finally started to make PC's cost effective for enterprise.
Even today, you can still see echoes of their stumbling attempts to appeal to enterprise users, but a focus on small business, with some of the legacy networking components still built into Windows, like WINS.