I saw the news on Facebook yesterday, and it was a shocking firing; however, it wasn't surprising. Although I think they could've given him until the end of the year to see the end result of this year's campaign.
The Kings have been very disappointing for the past season and a half after being projected to be among the West's rising teams such as the Thunder, Rockets, etc. It's not all Mike Brown's fault but it's easier to put the onus on the coach because are you gonna trade away your best players (Fox, Sabonis, Murray, Monk, etc) for underperforming? No, so the coach is the one who can easily be the expendable asset, if necessary.
Sure, since Mike Brown's arrival, even with the dismal play, they have been far better than what they were for the past decade, and then some, so it's not all bad, but the ceiling had gotten higher after making it to the Postseason as the 3rd seed and losing a highly competitive 7-game first-round series against the Warriors that inevitably came with a lot of expectations for the next few seasons.
The Kings should be better than what they are currently; they're kinda like the Pelicans in that, on paper, they have the roster to be at least a top 4 or 5 team in the West, but their play has been underwhelming.