It's not typical for the board to directly intervene with the affairs for the company, but it's still far less unprecedented than making the most important decision in their history while deliberately excluding a third of the members. For example, a year before Yahoo fired Marissa Mayer, the board appointed a committee to explore "strategic alternatives" with management.

https://www.businessinsider.com/marissa-mayer-yahoo-meeting-...

Which is absolutely different than changing the corporate structure.

What the Yahoo Board was doing was essentially bringing in their own set of advisers.

As the other comment said, the strategic alternatives plan had nothing to do with firing Mayer. It was specifically about how they could unload their Alibaba equity without triggering a huge tax bill.

But regardless, the board had six members. Altman was actively trying to grow the board (and would presumably add loyal allies), and had previously tried to kick Toner off the board. So just by sheer numbers it's obvious they had to move quietly before they acted. And you saying this is "unprecedented" is just weird - CEOs are fired with little warning all the time, and if they also have board seats, the board members who want to fire them usually figure out if they have enough support before hand.

I think the thing we're probably agreeing on is that the board just handled the communication abysmally. I don't know how they thought they could fire Altman without a detailed explanation, especially to their partners like MS.