My private details leaking is damage, that's the point here. If I trust you with my confidential details (which can be anything from my bank details to my email

My private details leaking is damage, that's the point here. If I trust you with my confidential details (which can be anything from my bank details to my email address), and your data security protocols mean that my data gets stolen, then I have suffered damages, and GDPR comes into play.