for example in this case you should first discuss the reasons why a government or bank would want to control 90% of bitcoin supply? is it to control its price and make profit? or is it to control its future development? or some sort of censoring?
I am a believer of the idea that Bitcoin will become a global reserve currency one days, that governments and corporations would be willing to make the most important of their transactions with because of its security, finality, and immutability.
The motivation would be the same as what they do to other valuable assets. Try to corner its market.
What? Controlling 90% of the supply would make it stop from being a permissionless system.