I think that the Apple/Google/Microsoft/IBM quadrifecta perfectly illustrates one of the lesser-known points of
The Innovator's Dilemma: customers care about different values in different points of the product's lifecycle, and that leads to differing companies becoming dominant.
When a new product category is introduced, customers primarily care about ease of use and relevance to their lives. Radical vertical integration is usually necessary to achieve this, because any friction in the product's interface is on top of the friction of getting consumers to use a product that they're completely unfamiliar with. Hence, the market is totally dominated by one company that makes everything from the chips to the hardware to the OS to the apps. This is Apple. This is the Apple II in 1976, the Mac in 1985, the iPhone in 2007, the iPad in 2010, and now the Apple Watch in 2015. (It's also Netscape in 1993, Yahoo in 1998, Amazon in the early 2000s, and AWS today.)
As the market matures, more competitors enter. An ecosystem of third-party apps develops. Hardware supplier prices drop as more hardware manufacturers develop expertise and enter the market. Customers start to value compatibility, options, customizability, and adherence to standards over raw ease of use. This is Google now and was Microsoft in the 80s & 90s. This is MS-DOS in 1981, and Windows 3.1 in 1991, and IE5 in 1999, Google Search in 2000, Chrome in 2008, and Android in 2011-present.
Eventually the technology moves up-market. Customers start to care more about security, stability, reliability, and performance. That's Microsoft now and IBM in the 70s & 80s. That's mainframes in the 80s, and MS Office and Win7 now. At this point, the technology is already being disrupted, but the disruptive technology isn't reliable enough for a segment of the market.
Finally, you get to the point where customers care about brand and compatibility with existing installations. This is maintenance work, where the company becomes a consulting outfit to keep all the technologies they invented a generation ago running. That's IBM now.