They needed a contender for Aldo, interim champs are usually always contenders, Holloway has had 9 wins in a row yet no shots so he deserves to be in that running, and they need a backup plan in case Aldo can't or won't defend. (Last point is important because Aldo, the last time he publicly made a statement, said he was retired if he couldn't fight Conor next, which obviously isn't going to happen. Conor's moved on, the division must too, and there's a chance it might do so two champions later)
A mess of a situation for all involved that would have easily been avoided if they didn't trust one guy over everyone else. A mistake the UFC constantly runs into, and will never learn from and avoid.