Consider the alternate history where fungi never evolved the ability to digest lignin, the tough woody material found in many plants. The period of time where plants could produce lignin, but fungi couldn't break it down resulted in the massive coal deposits found in the earth. Some bacteria can break down lignin, but they require wet conditions to do this. This is what happens in the gut of termites. So, of course, we can imagine an alternate history where termites rule the earth.