Both are true. The board as a whole is his boss in his role as CEO. He is the board's boss in his role as majority shareholder. That makes the situation a little less clear.
I don't think a court examining the board's removal of matt would conclude they acted improperly based on some gross simplification to "the role as majority shareholder role wins", that's why the board was able to legally remove matt. They made the right call, and matt subsequently made a different call in removing them because he was mad and full of himself. Both calls seem technically legal.