Why does MySQL stop working after updates on macOS Big Sur?

Question

MySQL

As upgraded to BigSur, each subsequent upgrade breaks mysql (5.6.35 MySQL Community Server (GPL)). It just stops seeing the root user, writes the password access is denied.

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

You have to take files from the backup directory usr/local/var/mysqland replace them with new ones, then everything starts working again. Can this be fixed somehow?