Rethinking this a little bit, the Bucks are already over the cap, so letting Tucker go doesn't free up any cap money. In fact, there was an advantage to signing him even if you ended up trading him later because it would preserve that salary amount for another player down the road. This was all about saving money for Lasry and Edens.
I know it's not my money, but Lasry and Edens are worth about 3 billion together. Not resigning Tucker probably saves them about 30 million over 2 years. That's still a lot of money, but it's analogous to a well-off middle-class retiree with a net worth of 1 million deciding not to spend $10,000 on something nice for their family. It's a defensible business decision, but it's a bad look for an ownership group that promised to spend into the luxury tax to optimize winning over the long haul.