Banking is control. If there is one certainty, the bigger the bank the more control it wields. So it logically follows that one big bank to control all the money would be exceptionally harmful to the non-bankers of this world.

I've read somewhere.... Power corrupts (look around you folks)... absolute power corrupts absolutely. Look at history. Precious few examples of any "rulers" that were exceptions to this idiom. Trump is one. Let us all hope he finishes the job and his successor is not prone to reversing field.