I don't know that he was unhappy in the bullpen, the contract was heavily biased towards starting and he would certainly want to try to maximize that. No one will be able to say the the Twins didn't give him every chance to be a starter but after an excellent short season, a long TJ recovery and now fatigue its time to have the conversation. He has to perform, especially when there is very stiff competition. He can be a weapon out of the bullpen and Ober can get in the rotation.
There is no such thing as too much pitching but there can be too much of the wrong type grouped at the wrong time. It puzzles me how the Marlins and the Reds can stink on ice but be like Oprah passing out pitching to everyone.
I would be on the lookout for a trade from our starting pitcher reserves somewhere this year. Mahle more likely than Maeda but also Ober, Varland and SWR as the return would be much higher. Hell, throw a couple young starters, Kepler and Gordon at the Pirates for Bryan Reynolds and low prospects. Varland for a Burnes rental? A guy can dream.