Luka being out another week is probably why Dallas did this trade. Hindsight is 20/20 as they say, if 5 years down the line, we see Luka keep being injured all the time, then we could probably see this be a good trade in the end for Dallas.
I mean don't get me wrong, they could have still gotten someone better for Luka, not AD, but I am pretty sure that if Luka fails to play more, and just gets injured all the time and turns into Neymar situation, then yeah this will be a bad trade for Lakers. But we still don't know, we just know that he is out, and the claim is that he is "fat" now, but I do not know anything else about his situation, this is something we can't know right away, we need to just wait and see how it works out.
We will find it out once he start playing for the team, if they performed better compared to how they perform with AD then it's going to be a good trade, but if not then maybe they are just bringing the hype and is business as usual, Luka is Luka we all know that LeBron is nearing or close to his retirement and pairing him with Luka will gain sales in terms of tickets and merchandize,
A young superstar together with the top scorer of the league, that's equal to good ticket sales, a decent amount of money for the franchise.
It's a bonus for the fans if both will perform well and will bring the team to another finals then win another title.