There's no need for me to prove that this can happen because, as I pointed out, it already has happened many times, from Xerox to HP to Dell to IBM. It's happening right now at Oracle. You can see the very earliest stages at Apple and Google.
Apple and Google control the internet, through controlling web search and browsing. One pays the other to ensure this monopoly. And none of the companies you mentioned were worth 3 trillion, and last I checked they all continue to exist and hold reasonable market share, and none of them taking market share from another is a case of a garage startup knocking off a monopolist.
The modern tech company is more akin to Standard Oil, but possibly even more powerful and all encompassing considering Google for example can determine what is true and false for a given population. Standard Oil was only able to be toppled by a State.
So again, what capitalist mechanism exists to allow a garage startup to knock over apple or Google? I completely agree with you that Google is enshittifying - my disagreement is that anything will happen about that unless a State intervenes.
