The best thing about "tech monopolies" is that there are so many of them
Messaging? FB vs Apple vs Google
Ads? FB vs Google vs Amazon
Video? FB vs Google (YouTube) vs Amazon (Twitch)
Especially re: Google linking to its own sites, are we now arguing Google has a monopoly over google.com? It gets a bit weird
Search? Google. Online retail? Amazon. Video hosting? Google.
I don't know anyone who's arguing that. But I do see people arguing Google having a monopoly on search. In a lot of domains, a business can be created or destroyed entirely on their Google search rank.
The competition just isn't as good at search. Bing has been around for a long time and has managed to gain less than 10% of market share, even though almost everyone has heard of it.