IMO just like with the THT trade, the simplest explanation is probably the right one - Ainge just loves Kelly Olynyk more than anyone else in the world. With old school GMs that's a recurring theme and one we should be ready for in the future. Ainge will make some head scratcher moves simply because he has his evaluation and doesn't go a step deeper and ask himself - are others seeing it this way and can I actually get more here? He was reportedly ready to trade 4 1sts for Justise Winslow. He also traded out of no. 1 pick when there was a consensus best player(and was right in that case), he also drafted Brown no. 4 when nobody wanted him this high. He just has his views and sticks with them even if unpopular.
I personally hate this deal. And the worst thing is - it signifies we probably won't be able to get anything of value for the other vets.
Ainge ran out of gas and is now just shooting from the hip as we get closer to training camp.
Analysis, meticulous strategy, and tough negotiation has gone out the window. In the wake of getting so much for Rudy and Donovan, the analysis now is "well we kinda need to move off the incumbent guys and we should save money in the process. Also, I just kinda have a boner for certain guys, so, IDK."