What a ridiculous comparison without context. In 2018, EFF's total support & revenue was 17.2M ($15M being public support) [0].
In 2019, the Linux foundation had $96 million in revenue and $71 million in assets [1].
In 2018, Mozilla's revenue was $450M [2].
So how could you possibly compare EFF CEO's pay to Mozilla's? If Mozilla's CEO performs 10% better than the market average CEO, that's significantly more valuable than if the same thing occurs at EFF.
The market rate of good CEO's doesn't simply decline because they work for a non-profit. It depends on the context.