Not half, all of your time will be busting your ass building up rapport.

Lets look at the alternative: you start a greenfield project with no understanding of what the rest of the company's stack looks like. Engineers know some person was hired to do something, and they may be interested in what you're doing, but they're probably not invested in it (the people who hired you are probably more invested, but they're unlikely to be the ones who have a deep understanding of the tech stack). You're facing an incredibly uphill battle here, as there are certainly going to be things that you will need assistance with (custom libraries, weird deployment frameworks, shitty deployment scripts that only one person somewhere knows how to get working etc.).

You may be a super genius, super hardworking person and be able to pull it off. For the average case, I am convinced this is a backwards way to approach the problem.

It doesn’t prevent you from using personal power and influence, although most organizations are setup to purposefully make it difficult to function that way.

Usually your best managers do both. Think of the best people that you’ve worked for in any environment. Usually they are people from whom you’d seek advice and counsel.

That's a pretty simplistic idea of how a manager wields influence imo.