I don't think that monopolism is at the heart of Silicon Valley's "growth through innovation". Big tech companies stifle real innovation more than foster it. In any case, that wasn't the thrust of the article.
What I read in the article was that the political class is concerned about how these tech giants are moving into much larger spheres of influence, such as Facebook's role in the election of Trump. Google is getting downright scary when they control not only how information is retrieved but is now manipulating and guiding what information goes to each user. Taken together, what the big three (Google, Amazon, Facebook) know about each person and what they can do with that information is practically unbounded because our privacy laws suck.
Anti-trust laws are in place to prevent companies from unfairly controlling markets. While they pose a corporate threat to existing power structures, I'm not aware of them breaking anti-trust laws, like Microsoft did in the '80's, so what's with the reference to monopoly?