Here is my read on the situation (with a lot of speculation)
Dame thinks that the Blazers weren't actually trying to put a contender around him. I don't think that's true... at least not at first. Last summer Joe went out and got Jerami Grant and GP2. Those are not rebuilding moves. Those are moves to make Dame happy. Those were better moves than anything Neil did in the last four years. I wasn't a fan of GP2, but he clearly was a "win now" move. Unfortunately it didn't work and the team still sucked. It made sense to tank and try to acquire another asset. The odds were that we most likely would not have a great pick in this draft, but fortune shined on us and got us the 3rd pick.
Lots of credible sources have said that Joe did attempt to move the pick and build around Dame. Other people claim that Joe didn't really try and most of the offers he made were disingenuous. This is one of those points that will be nearly impossible to prove either way. Dame most likely hurt the value of the pick by saying, for all intents and purposes, that he'd demand a trade if they used the pick. This is the first example of Dame making Joe's job harder. If Joe was actually trying to move the pick, this had to hurt his leverage in negotiations.
I think the path diverges here. If I'm the Blazers, I'm looking at this young superstar replacement for my aging HOF point guard and I'm thinking it's time to move on. Joe isn't an idiot. He knows that he can't build a contender around Dame in a few years time. When he couldn't flip the pick, that was the death sentence for Dame in Portland and I think both sides knew it. This is the point where they should have come together amicably and just worked out a solution where everyone leaves happy. Unfortunately that's not what happened.
What we do know, through reports, is that Dame requested a trade to only one city, and his agent did everything in his power to make it more difficult for the Blazers to trade Dame. The Heat gave a lowball offer. The Blazers didn't want to deal with Miami. Possibly because they didn't think the Heat had anything they wanted. Possibly because they didn't like being bullied into only one destination. Possibly because they felt like Miami had tampered. Either way, the Blazers weren't motivated to get something done with the Heat.
There was a report that the Blazers filed a grievance against Dame and his agent. Haynes reported that the NBA had a meeting with both sides and lawyers were involved. To me, this indicates that there is A LOT more to this story. If Joe was THAT pissed at Dame, there is clearly more to this that we have not heard. Maybe we won't ever hear about it. The Blazers haven't been airing their dirty laundry like Dame has. I just wish people would recognize that there has been transgressions from both sides, everyone is pissed, and I don't think there's an innocent person in this ordeal.
I just want to move on and be excited about the new team.