Gates is often credited with the standardisation that the IBM PC and its clones brought about, as compared with the chaos of the pre-PC micros. However, this standardisation (such as it is) is due to the hardware - which is not Microsoft's area. It occurred because people wanted standardisation, and when IBM entered the personal computer market the architecture of its hardware was increasingly adopted as the de-facto standard.
Other companies could legally make clones of the IBM PC because IBM did not patent or restrict use of its standards; they took this liberal approach in order to give themselves a broad base of component suppliers, simply because they did not have the capacity to make everything themselves. Also, IBM did not take personal computers entirely seriously at that time.
Soon, independent electronics companies, whether suppliers to IBM or not, were making IBM PC compatible components such as memory and expansion cards for networking and graphics, and in due course even motherboards and the central processor. Using these components, a PC-building cottage industry sprang up and flourished from about 1985, assembling "IBM clone" PCs from independently made components and undercutting IBM's prices. The smaller these PC building comapnies were, the more anxious they were to keep to the de-facto IBM PC standard in order to be in this market. Unlike the pre-PC micros, the IBM PC and its clones could run the same software as each other and by the early 1990's had displaced almost all other micros from the market.
Similarly, there was a loophole in Microsoft's contract with IBM which allowed them to sell DOS (rebranded as MS-DOS) to anyone else. In this, Microsoft's position was no different from any other PC component maker. So the PC clones were generally installed with the readily available MS-DOS to maintain compatibility with the rest of the IBM PC clone market. The same would have happened with whatever operating system supplier IBM had chosen, from Seattle Computer Products for example.
Thus it was IBM's liberal policy, not Gates, that brought standardisation to the personal computer scene. In fact, Gates and his company have generally disliked cross-industry standardisation, prefering users to be locked into the Microsoft eco-system (usually under the euphemism of an "enriched experience").
As a footnote, The main non-PC survivor through this IBM-compatible PC period has been the Apple Macintosh. This and other recently emerged alternatives, such as Android devices, mostly run some form of Unix, an operating system that preceded DOS and on which personal computers might have standardised thirty years ago if it were not for Gates.