The CMO tenure statistics are not a mystery. They are arithmetic.
The average CMO in a digital business at serious scale lasts between eighteen and twenty-four months. Not because CMOs are poor performers. Because the role is structured to absorb accountability for commercial outcomes it does not fully control, and the clock starts running from day one regardless of what the CMO inherited.
Think of it as being asked to conduct an orchestra where half the musicians were hired before you arrived, are playing from a score you did not write, through instruments that were not tuned before you took the podium. The audience still expects a performance. The board still expects results by Q3. And when the sound is not right, the conductor is the most visible person in the room.
The businesses where CMOs last and compound their impact are not the ones with easier markets or bigger budgets. They are the ones where the commercial system the CMO operates inside has been honestly assessed from outside before the CMO is asked to perform inside it.
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