Their decisions are absolutely constrained by the system's values. They have zero agency in this, and are literally unable to imagine anything different.
There's no total ownership in structures as large as this - neither in companies nor in countries. There are other stakeholders, and then the organization has a mind of its own, and they all react to actions of whoever is nominally "running it".
The truth is, no one just acquires power on their own - people with power have it because other people let them, and they can wield this power only as long, and only in ways, as others allow it. Gaining power doesn't make one more free to exercise it - on the contrary, the more power you have, the more constrained you are by interests of those who provide you that power.