i'm just guessing here but i think that the critical requirements to be able to run banking apps securely on your smartphone are:
- lockable/unlockable bootloader
- quality control of the operating system to make sure it doesn't contain malware/spyware
- internet connection & open-protocol banking network
the first two parts are general smartphone/laptop security and operating system integrity, which can only be done through hardware/general software developers. Like i think we need reliable hardware manufacturers but also institutions that check that open source software doesn't contain malware. Like when you run apt install some-package who says that some-package doesn't contain malware?
The third one is the only part that is actually specific to banking. That's a whole separate topic and has barely anything to do with the first two steps.