Giannis will said that Thanasis is part of his development that's why Bucks decide to sign back Thanasis and give him minimum veteran contract.
Bucks will not really got hurt on the contract he give on Thanasis and they became more stronger now especially when they get those new players on their team.
Also it seems that current Bucks roster is much stronger than what they have last season.
Sure, the money won't hurt them but still it's a waste of a roster spot, which is also limited. The only upside it keeping Giannis happy, everything else is not worth talking about. These nepotism moves that get more and more normal in the NBA are quite sad in my opinion. Sure, it's just a way to keep your most valuable asset happy, still it's taking away opportunities of real NBA players that have far more skill that certain guys that land a spot through family connections.