g-suite ate a huge chunk of Exchange's lunch, and a non-trivial part of the office lunch.
ChromeOS ate a nontrivial part of Microsoft's OS business.
Android completely obliterated any chance of a market MS had for phones.
Chrome (and Firefox, which was effectively funded by Google for a long time) dethroned IE(and edge), almost to the point of irrelevance.
It did not disrupt Microsoft's business model - but it ate huge chunks of it. Where Google didn't venture (e.g. database & server software), Microsoft is still extracting monopoly rent. Where it did (mobile OS), no one wanted Microsoft's offering, regardless of getting free money with it.
Facebook and Google totally, completely, compete with each other. If you have on-line advertising spend, you decice on the facebook/google split. They are in exactly the same vertical - extremely directed and trackable on line advertising. Don't confuse "users" with "customers".
Intel's business model was expensive high margin CPUs to all. They still do for servers. It was most definitely disrupted in the consumer space because phones exist - many people for which it would have been unthinkable a few years ago to have no PC/Laptop today, only have a phone, or have a very loe end laptop (which Intel makes very little on).
> it was a new line of business opening up, due to changes in the market place - where a major player in a related marketplace failed to achieve dominance
You have just given the usual definition of disruption. I agree existing markets were not overtaken. Mobile phones disrupted the land line business, even though that one is still alive. Linux disrupted the proprietary OS bbusines, even though that one is still alive. Amazon disrupted commerce.
Facebook killed myspace, and yahoo participated in its own killing. And there's definitely disruption all over.