Cody is a smart kid... he knows now that Cody Rhodes, good as he can be isn't going to cut it... He's not gonna be World Champion under his own "name" or close to it.
He's watched his brother for 20 years in just a few short months and how he was in the same position in WCW... mid card at best, never living up to the family name. and Dustin actually stepped outside and forged something.
Whether you feel Goldust is more valuable than Duthy was in terms of titles... in terms of longevity and money earned he IS.. Goldust has earned more in his career than his father ever did and that is a grim reality within that family. Cody had a choice, adapt or "die" in terms of the business.
So he noticed the opportunity, Dustin is retired bar the shouting, good as he is still he's too old to carry on...so there is a gap in the WWE market, cos Kane, Taker, Goldust all those storied "characters" will be gone soon. So he came up with Stardust, the natural replacement to Goldust.
Make no mistake, Cody as himself bombs now, gets released etc... Stardust? He can sell merch, be around like Goldust was for years to come, not as a main eventer, but as a solid mid/upper midcarder as needed. 20 years on WWE money is worth more than 1 year as a transitional champ... Cody knows it, he's seen it... so why would he "need a bone?" he worked it out for himself... Fill the gap left by all these vets including your own bro and you can fill it for as long as they did if you're good at it and can see past the shiny belt thing that Rollins has...and he is VERY good at that character... Stardust could be around as a Tag Champ/IC/US champ like Goldust was for years... Cody? 3-4 years at best and he's gone... not to say he won't have "spells" as Cody... but really look at it coldly... if you could chose, be WWE champion for a few months, once... or 10+ years (and he is getting near that time ALREADY) with 10 more under a "gimmick", which are you gonna take? If you take the title, you're dumb as fuck...