Example: now that Google says that they don't mine email / calendar / docs data for ads, that means they don't make direct revenue from those services - unless a user pays for them directly a la G Suite or Google Drive pricing. Therefore Google leverages strong market share and revenue from Search to invest in these services to bundle them and offer them for free.
In theory any other company can build individual blocks, but most likely could not (1) offer them for free, nor (2) address the switching cost that a user of Google's services does not have (i.e. having multiple tabs or different applications opened to use email + calendar + files + etc.) If this wasn't a technology company, but like a p&g company, hypothetically, this would be clear cut monopolistic behavior.
That said, it's a thorny issue and I could see both sides, and the technology market landscape necessitates an analysis of our definitions of monopoly / market share / competition, etc.
In my mind search, email, calendar, cloud, drive are all separate services. Just because I use Google Search doesn't mean I use google drive and gmail. In fact, I use Microsoft's OneDrive most of the time instead of Google Drive, and I don't use Calendar at all (much prefer Outlook).
You do not have to build out that entire list to compete with Google - you can build and compete with a superior version of just one. Even indie developers can (and do - successfully) compete with services like Calendar.