I think the key point here is that Redbox did not buy a digital license from Disney. They bought a box with a DVD and a piece of paper with a code that can be redeemed for a digital license. They rent out the DVD and sell the piece of paper. Both of these are allowed under the first sale doctrine. Disney tried to tack on additional conditions to using the code on the piece of paper which the judge called "improper leveraging of Disney’s copyright in the digital content to restrict secondary transfers of physical copies".