> They are also given out for a number of other reasons. For example, when someone is perceived as a flight risk, because it makes their manager look good to promote their team, because someone has been given a lot of responsibility, whether or not they're good at handling it, because it's good for team morale to show that promotion is achievable, or because it can make a headache go away for the manager.
Big tech company is a huge group that has widely different cultures. Based on these reasons you listed, you likely didn't work at a FAANG or similar company (Uber, Doordash, Lyft, Airbnb...etc). The reasons you listed are responsible for 0% of Staff promotions at these companies (except the "given a lot of responsibility they're not good at handing" reason you gave, assuming the person is taking credit for other people).
I agree that all of your reasons are valid for Senior and lower promotions, but these companies take Staff+ to another level by using a completely different promotion process beyond Senior level (even L5B or Senior II at Uber uses the more strict process).
The reason you see the "Jedi-like" trope is because the strict bar set for Staff plus promotions at these companies. To be fair this Jedi trope is created by the perception of other engineers because of the difficulty of achieving these levels and not knowing what it takes to do it. Career advice including this StaffEng book actually lessen the trope because it makes it clear how you can get these roles and removes all the mystique around the unknown.
The root cause for promotions occurring for the reasons you listed are due to promotion decisions being owned by just the manager or only a single chain of command (manger's manager, director..etc). This is how Senior and lower promotions also work at these FAANG+ companies. To get rid of that bias and gaming, all Staff plus promotions go through a promotion committee, and your manager has no power aside from submitting your promo packet to the committee.
No matter how bad the manager or his director of even Senior director wants to keep the employee or look good, they have no say in the promotion decision. There is a calibration process that ranks all engineers submitted to the committee against each other and only approves a small % at the top rank. Someone who got Staff promo this year might not have next year depending on the competition.
None of this is to say that the process is perfect or removes all bias. But the process is very strict and the promo comitte vigorously applies the rubric which is why you see all of this advice to exhibit skills typical on these rubrics.