To be honest, they should be afraid of their money stored, the existence of quantum computers will make bitcoin the safest assets, because logically banking is easier to break, because the banking system of the security system is not as long as it is on Bitcoin.
The people were not aware of their position, they frightened Bitcoin but had no awareness of the security of their money at the bank.
Although I don't believe in quantum computers because everything is still just rumors, so far. But I think if it can pose a threat to the banking system, bitcoin will be hard pressed to avoid those threats as well.
Banking is a centralized system and upgrading becomes easier when it does not require community consensus, and is protected by laws and governments. So it is very unlikely that quantum computers could threaten them.
To be fair, bitcoin and banking are the safest and most secure systems in the world because they use the same powerful algorithms, and both have their own pros and cons. So if quantum computer could decode those algorithms, both would be at risk, not just one.