This is a more reasonable take. A single bad app launch cannot be the sole cause of a company falling apart to the point where they need to fire the CEO.

Boards are typically loyal to their CEOs (if the stock and revenue are performing well). They'll never fire a CEO who's coming out of a double-digit percentage growth last quarter.

Thus, the reason he fell out of the boards' favor is the low performance primarily and this was the last straw indeed.