Banks don't have money today because they worked hard and sweated and laboured tirelessly for every single dollar in their vaults....banks survive a la GFC, because the government gives them a license to print dollars into existence and then underwrites them with implicit guarantees (taxpayer funded).  Banks take the dollar you give them then they rehypothecate it / fractionally reserve lend it into being 10 or 100 dollars as loans to mortgage owners (you and me, who are silly enough to slave away at our cubicle farms for forty years to pay back a mortgage debt plus fat interest) or as loans to businesses (who use lawyers to pass the buck to bag holders, a la Bernie Madoff).
So yes, banks have lots of money TODAY to potentially path into crypto currencies....but will they?  ....can they? .....given how they need to externalise their problems onto bagholders.  This ship will sail.
Banks are a 20th century legacy idea, 21st century will replace banks....with something like cryptocoins or their successor.
Banks are an idea whose 'use by' date has arrived.