It is very possible that the owner has a recurring payment in place, or that the owner renews after it expires. Because GoDaddy gives a redemption period like all registrar, many domain name investors will actually allow their domains to go through auction to see what the “market value” is of a domain name and THEN renew it. It sucks if you’re the buyer thinking you won the auction. It happens often, unfortunately.
Finally, just because you have an idea doesn’t mean that you have more rights to a domain name. That’s not the way the system works. For example, Microsoft owns more than 75,000 domain names. Surely they’re not using them all — but they were acquired through purchasing businesses, hand registering them for business ideas, defensively registering them, etc. And they have the right to do so, just like you do for any idea that they have yet to come up with…just like a real estate investor does for a plot of land they have no intention of building upon for the next decade…just like an art collector does who wraps a Picasso and puts it in their basement.