[namelessoracle]

Sure, there's also the point that while the junior to staff has connections, they might have also earned enemies too which will seek to impede stuff they want done. Where as the new staff has a fresh slate with everyone.

Generally speaking though, people i've seen promoted to Staff are more effective at the role than people who come in at the role, because Staff seems heavily weighted towards being able to influence at most companies. And being a known quantity counts for a lot. (also to become a staff someone higher in the food chain had to have already vouched for you and be willing to grant you some degree of patronage)

Also the value prop for what you are saying of "new pattern or practice" only applies if the staff gets to do green field dev, its rare a brand new staff without political capital can force a pivot on an already in development product that has patterns already set. In short its rare it gets to manifest, and when it does get to manifest it can take a year or 2 to manifest, and people who are willing to jump into staff roles probably have their next spot picked up for their next salary hike already picked out ;)