If you don't think there would be a shareholder revolt against the board, for simply exercising their most fundamental right to fire the CEO, I think you're missing part the picture.
Developer platform updates seem to be inline.
And in any case, the board also failed to specify how their action furthered the mission of the company.
From all appearances, it appeared to damage the mission of the company. (If for no other reason that it dissolve the company and gave everything to MSFT.)