Some teams are willing to have a higher turn-over of talent (assets) on their rosters. The Jazz seem less willing to do this. If they're going to trade for a guy like Mirotic, they want to know that he'll fit into their plans and cap strategy longer term. They're considering things like minutes distribution, pecking order, shot distribution, chemistry, etc.
Another factor here is that the Jazz were looking to trade out Rodney Hood rather than have to retain him in free agency. They were likely in discussions with Cleveland at the same time for Crowder, a player that they liked. So they flipped Hood for Crowder without giving up a 1st-round pick.
You can think of it this way: the Jazz used their assets to get Jae Crowder and Grayson Allen instead of getting Mirotic. Now maybe the Jazz could have gotten both Mirotic and Crowder, but then there'd be a bit of a log-jam at the forward spot, and less cap room for 2019 free agency.
