Put yourself in Daniel's shoes. You have done everything you need to accomplish in MMA. You have become the champion because Jon Jones was gone.
You finally get to fight Jon Jones again but you lose. There is nothing else to do. You are simply 2nd place. You are older, and can only get worst. The next logical step is to accept that you lost to the GOAT and that's all there is to it.
What's the point of fighting a couple more years to get another title shot when you are even older and get beat up worst.
You can't go down to middleweight because you don't have the discipline to lose that belly. You can't go to heavyweight because you are either fighting Cain, who is the gym alpha, or you will be fighting the guy who KOed the gym alpha. There is nothing you can do at this point.
You finally get to fight Jon Jones again but you lose. There is nothing else to do. You are simply 2nd place. You are older, and can only get worst. The next logical step is to accept that you lost to the GOAT and that's all there is to it.
What's the point of fighting a couple more years to get another title shot when you are even older and get beat up worst.
You can't go down to middleweight because you don't have the discipline to lose that belly. You can't go to heavyweight because you are either fighting Cain, who is the gym alpha, or you will be fighting the guy who KOed the gym alpha. There is nothing you can do at this point.