How would you split Google into entities that won't go bankrupt within a year? ( And you wouldn't want that because it would piss off people and would help the cause of the anti-regulation and anti-government uneducated people). Maybe GCP, Android foundation, YouTube, rest of Google could work, but the "rest of Google" is still too big and too powerful.
Forcing them to open their data and platforms ( e.g. allowing other ad networks to access Google's tracking data and to serve ads via them) could diminish their monopoly, but it could also diminish their profits and force them to cut some less profitable parts of the company even more ( and that might be good).
Same thing with Facebook, just a bit easier - splitting off Instagram and Whatsapp will absolutely improve things, but the remainder is still to big and powerful. Twitter is even worse, you can't split anything.
Anti-monopoly laws and frameworks need to be updated for the modern world, because the logic that worked for physical assets, sales and infrastructure ( e.g. the US split oil companies and telcos along physical lines) no longer works for Internet companies.
Many power companies have government enforced monopolies across the US. They also are heavily regulated and limited in what they can do to prevent them using their monopoly to extort, abuse, or neglect consumers.