The breach of the WordPress credentials is bad, as is the sFTP credentials. Sure, if you are still using the same WordPress password that GoDaddy assigned to you when you started the account, you really need to step up your game.
WordPress is an inviting target, because getting admin access to a WordPress install, or really any other content management system, makes it super easy to lock out the original owner and inject anything you want into the site. Want a place to spread malware in drive-by injections? Nothing like an already existing, and maybe even trusted, WordPress site, eh?