Oda makes some interesting commentary over the course of this flashback. All indications point to Sabo's family being ridiculously wealthy and powerful--they're not pushing Sabo to marry into the royal family because they're an impoverished family with a noble name, for example. Even after Sabo's family succeeds in making Stelly king, the first thing he tries to do at the Reverie is sit on the Empty Throne. They have everything they could ever want, but it's not enough.
Bluejam is the same. He's a successful pirate captain with a loyal crew, but sells himself to the royal house on the promise of being made an aristocrat.
Then there's the king himself, the leader of a prosperous and apparently peaceful nation, who sets an enormous fire in order to clean up the mess he made and hopefully kill a few undesirables along the way, all in order to cozy up to the Celestial Dragons.
Next chapter Sabo will link this "stench" of the Goa Kingdom to his own lack of freedom. One Piece is a series that prizes ambition, but this flashback shows the dark side of this sort of social ladder climbing. It argues that true freedom doesn't come from stomping other people down while you try to climb your way up toward reaching your dreams.
