They weren't going to win a championship with Jrue Holiday. The fact is that they needed someone like Lillard to get a bucket when teams clog the paint with good defenders in the playoffs. We've seen what happens when the only path is Giannis barreling in on every possession. Middleton can no longer be counted on and Pat Connaughton/Bobby Portis isn't that guy.
Jrue Holiday wasn't the problem (although his too frequent 6-of-22 nights were), but he is the only asset they had that would have brought something like Lillard back. I think every Bucks fan knew they were going to miss Holiday and everyone would have preferred sending Middleton off for that kind of ROI, but it was never going to happen.
It was either run it back and know they aren't going to win, or change course with another superstar offensive player and see if it helps. I think the jury is still out. I think it's likely they flame out, but being the NBA I would still wait and see what happens when everyone turns on another gear in the playoffs. We haven't gotten what he needed to get out of Dame, but I think the trade had to happen. There had to be a shift, whether it works or not isn't relevant to me because I know they weren't going to do it with Holiday.