Harden was signed to a minor league contract by the Twins in December. Included in his contract was the provision that he could be released if he wasn't on the Major League roster by July 31. Considering he had yet to throw a pitch in a game for any Twins affiliate, that wasn't going to happen.
With that fact in mind, it's interesting that Harden asked for his release. The potential for him to find another interested club who would be willing to have him pitch for the Major League team in the near future is all but impossible. Speculation could include that he was unhappy with how the Twins were dealing with his rehabilitation process, that he simply didn't think he had a chance to rebuild any value with Minnesota, or that he knows his body won't allow him to pitch this year - if ever again.
It's unfortunate that Harden wasn't able to get ready for the season. While the bullpen has been an asset so far, it would have been interesting to see how much talent was left in that arm.