There's such a wide variety of reasons why people object to what they see as too high salaries for CEOs.
Some people think it would mean there'd be more money to pay other, lower down staff. That's sometimes but not always true. As an example, the CEO I mentioned upthread was paid nothing. His incompetence absolutely prevented the charity from being able to apply for and likely obtain more funding than his salary would have been, iyswim, and he also pissed off several experienced paid staff who left, thus incurring substantial training and recruitment costs. Had we paid someone even 40k, we'd have obviously had higher staffing costs, but that would also have purchased competence and more funding. Put bluntly, sometimes when you pay someone more, they bring in more.
Equally, there are charities where it's a more fixed pot. And there are also no doubt examples of posts where the extra X amount on the CEO salary won't have resulted in better outcomes or more funding for the charity.
Then there are people who just think charity staff shouldn't be paid at all. Or should but only enough to cover the bare essentials. Or should be paid but only at some arbitrary, much less than is available elsewhere rate that they've just plucked out of thin air.
For these people, even something like only 10 x the full time rate of the lowest paid employee is going to be far too much. Bear in mind NMW FT now is above 15k, so the salary here isn't too far from 10 x that. It'd be less for apprentices, but more if the charity is paying eg the living wage. These are also people who are likely to be resistant to things like paying charity trustees, even where that has the potential to widen the pool beyond the Daves and Johns that disproportionately populate it now.