Banks are embarrassed by the current economic crisis. They are looking for a far-reaching and stable currency. USD can meet their needs. Where the value of the dollar fluctuates. But the value of the USD is almost fixed. They are choosing the path of reconciliation after not taking risks. For digitalis, they are motivated to enter the crypt world.
Just think they're only picking interest in stablecoin because that's the best competition to bitcoin in regards to the adoption of cryptocurrency. If there was any coin that can meet the need of the average users that doesn't want to deal with the traditional banking system anymore then stablecoin are the best alternative to go due to its stable form and less volatality.
With stablecoin the banks feels they can beat bitcoin. The total rate of transaction already recorded in the stablecoin market surpassed that of bitcoin at some point. So there's every possibility of stablecoin overthrowing bitcoin if the banks comes in. But this can only be in market capitalization and not in price appreciation.
Nevertheless since the banks backed stablecoin won't be decentralized they won't be any different form the current fiat systems in existence. What will be different is just their digitization.