Not sure if serious? Mavericks were a joke of a franchise before he was GM. He gave them Dirk, turned them into a perennial playoff team, got the players for the title. As Dirk's reign was clearly ending he somehow found a better player to be Dirk's successor. Hasn't been able to put players around Luka yet, but these things take time with young players. There's a couple good ways to put talent around great young players:
1. - stay bad long enough to keep getting more lottery picks. Luka made Dallas too good too quickly to go this route, similar to how Lebron made Cleveland good very quickly. So this is not really an option.
2. -bide your time, keep your cap flexible, and wait for the right free agent to become available. Aside from Porzingis, which at the time seemed like a good move to most, they have kept things pretty flexible. You just can't find another star to go next to a young superstar like Luka overnight, takes time and careful planning.
Donnie was good at identifying European talent, no doubt. Donnie had an eye in identifying talent before the league shifted over the last 10 years. And for the most part Donnie was, WAS, a good GM for a long time... But he has not been a good GM for years now. Easily going on a decade.
There is a reason Cuban and the franchise started listening to Bob Voulgaris, and it's because Donnie constantly fucked up over the last decade. He was terrible in the draft, outside of Luka and Brunson. Donnie really wanted Luka, as did Bob. But aside from that Donnie just missed way too often. Donnie traded away Seth Curry for Josh Richardson most recently. He also gave Dwight Powell $10million a year. He has a lengthy track record of heavily underperforming, in recent memory. Not to mention they wasted Dirk's last 6 years doing nothing. It is absolutely time to move on from him. Get someone who has better relationships with agents etc.
As for Carlisle: He is a great coach... But I'm perfectly fine with moving on from him as well. He is an X's & O's guy, and a damn good one, but this is a players league. The coach needs to be someone who can harbor young talent, and the players like... And one that potential free agents like. Free agents did not want to play for Rick. I strongly recommend this podcast (below) that Lowe did with Tim McMahon just hours before the Carlisle news broke. Tim does a great job of detailing the tension between Rick & Luka.
Also, the general media consensus in DFW right now is that Cuban is a retard and it's his fault, and you do whatever is happy to make Luka happy whatever that may be. Luka is super professional with these kind of things, and has said all the right things. He might not love Rick, he may hate Voulgaris, but kid is very mature. His job is basketball, and he is aware. I think more than anything the Cato/Athletic article was the final nail in the coffin for Cuban. I think he realized they need more results. He won't get blind loyalty from everyone like he did Dirk, sadly.
First 30 minutes or so is Mavs dysfunction talk.