Now that explains clearly why mine went through. I have 2fa setup with a complex password that hasn't been ever changed.I think you missed the point. To download and install the update, you must use your current Apple ID and current password. However, by doing that, the verification does not work because it is now trying to verify against your Apple ID and original password that was use to activate the iPad during its initial setup.
Thus, this is not an user error, but a software OS problem. A little more empathy and understanding please.