I didn't notice any link with the iPhone, except maybe a vague coincidence in timing. Online banking existed before the iPhone, it worked using websites, on personal computers. And it took some time before smartphones were taken seriously by banks.

What I noticed however is a noticeable decrease in service quality in bank branches while online (desktop browser) options became better. Banks pushed customers out of their branches progressively. In the early 2010s tellers couldn't do anything you couldn't do online by yourself. For services like dealing with large quantities of cash, or coins, they made it so that you couldn't do more than what the ATMs allowed you to do, limiting the amount of cash the branch had access to and increasing how much you could withdrew from ATMs.

They didn't get the idea to fire all their tellers when Steve Jobs announced the iPhone. It was a decision at least a decade in the making. It is just that people tend to resist change so it happens slowly, especially for big, serious business like banking. And I don't think it is a bad thing.