I get what you are saying but that's how it works in that world. CEO's get golden parachutes all the time after going scorched earth and making bad decision after bad decision. Absolutely had to fire him, no way around it. The whole franchise became a mockery based on one move, which he's responsible for.
I still believe some funny business was going on. Trading him to the biggest market in the NBA, for pretty much nothing, at like midnight on a random Saturday night. Nico has ties to LA. That was the only team that was contacted for this trade. Dallas then gets the #1 pick months later. Did the NBA put the call in to give the Lakers Luka and they'd reward Dallas with the #1 pick? With as crooked this league is, 100% plausible. If you want to trade Luka, wait until the summer and wait for the long line of suitors and make them bid against themselves. Dallas could have gotten a huge haul. Not a broken down AD and some throw in junk.
This was like trading Dirk the year after he lost to Miami in the Finals. Both right in the middle of their prime.