I think it will be very hard if not impossible for any entity to have a widespread effect on the larger fediverse, simply because we can defederate problematic servers.
The moment a Google instance comes online, a lot of servers will block it on principle. Then every time they do something new and scummy, more servers will block them. Eventually, enough of the network will have defederated from them that they just don't have any reach outside of their own server.
Not to mention that based on google's history, a mastodon server would last for maybe a year before Google gets bored and kills it.
Sure, google could set up a server with a billion people, but how can that have an effect when nobody outside of that server sees any of it?
If you wanted to force change on the fediverse, it'd probably have to be a massive undercover grassroots campaign. I'm talking spinning up hundreds of instances with a few thousand users each, and don't let anyone know that those instances are owned by Google. Then you play the long game where your users slowly influence other instances.
I just don't see that happening.
Every server in the fediverse is independent, and has its own culture. Thinking Google could cause change to all of those individual cultures is like saying if you put a few billion people in a new country it would change the global culture. Technically, yes, that could work on paper, but it doesn't really work in practice. Not on the sort of timescale any corporation is willing to invest in.