You wouldn't think that banks would be all that rich and powerful because their ostensible business model appears to be a rather simple one as all they seem to do is loan out money, make capital investments, create bonds, and add fees, but they don't actually have an actual tangible product that they manufacture and sell. Herein lies the rub, their product is money, to which they have unnatural advantages over their customers on virtually every level which they can leverage in all sorts of manners to their betterment and to the consumer's chagrin.
One of the massive advantages that banks have, that consumers do not have, is the fact that banks have access to money and assets through the fractional-reserve system. Essentially, the fractional-reserve system, allows banks to create money out of thin air and to thereby leverage deposits many-fold. That is to say, a deposit of $1,000 may only require that the bank actually have 10% or 12% in ready cash to back that money up and the balance can be invested, used as collateral, or swapped with other banks, so that this deposit with another bank, of 90% of $1000 or $900 will be treated as a new deposit and therefore that bank can loan out or invest 90% of $900 or $810 to another bank or subsidiary or virtual bank and so on and so forth. The long and short of it is, is that a deposit of $1000, gives the bank or banks the same leverage of having $9000, and it is this multiplier effect that enables banks to make bucketfuls of actual money, because their cost of money is so low and so cheap, in consideration of the 9x multiplier effect that they are literally making money off of other people's money and other people's labor, by for instance, charging an interest rate that is high enough to benefit the bank, but low enough that the customer can handle it while at the same time maintaining a margin which is quite comfortable for the bank.
In addition, banks get very rich, because the biggest debtor in America, the U.S. Government, borrows its funds from the Federal Reserve, which despite its name, is a consortium of private banking interests that acts as the U.S. Government's central bank. In any business, and especially in the money business, the entity that creates and controls the product is the entity that is going to be in the driver's seat of making money from that product. There is no better customer than the U.S. Government, because that is very citadel of power, which must itself feed thirstily from the central bank.
Further to the profitability of banks, we are all well aware of the new adage in regards to the biggest banks that they are "too big to fail" which means, no matter what fiscal mistakes that these banks make, that the game is fixed and that they will be bailed out by the U.S. Government, which makes these banks therefore theoretically unbreakable and consequently perpetual profit machines for the owners and stockholders of such.
It is said that money is power, and the banks hold and have the money, meaning quite clearly that they too have the power. These massive banks are truly in the catbird seat as to whether any of our Constitutional rights even matter, because with the capability to bring economic depression, recession, or hyper-inflation within their grasp, private wealth is at their mercy.