1) User goes to BAD website and signs up (with their user and password). BAD website captures the user and password
2) BAD website shows a fake authentication error, and redirects to GOOD website. Users is not very likely to notice.
3) BAD uses user and password to login to GOOD’s website as the user. BAD now has full access to the user’s GOOD account.
OK, with a password manager the user is more likely to notice they are in BAD website. Is that the advantage?