CEO pay is similar to other payments, where everyone is trying to claw themselves as much as they can, to certain personal limits. Powerful roles attract people who want power, and so, the higher up you go in a hierarchy, the more "
dark"[0] traits you find, which equates to lessening personal limits to power / money gain. If you think of the ability, willingness and perseverance of one to further one's personal power as merit, then this is a meritocracy after all.
With regards to accepting that, culture plays a big role. Governments effectively groom people into accepting the status quo, some stronger than others. They build on features of the human psyche that otherwise support this too, for example, in many cultures it's taboo to question elders, and also, many cultures observe different classes of people, where the different classes wield different levels of power by default. If you're interested in the psychology of this, I would suggest to look into how societies are organized over the recorded history of humankind.
The charisma and image of the well-off leaders also plays a part in making people accept, and support their advantage. This is also something that people are much cleverer about than in the past - the art that is currently called public relations. The idea here is that whatever people perceive, must make sense in their mind, somehow. If it makes sense, then it's accepted much easier, and if it doesn't, it's bothersome and makes people think about a story where it makes sense after all. So, one aspect of public relations is and making certain things observable, others obscured, and crafting a narrative about the observable things. This game is "history written by victors", but a bit backwards - whoever sells the most compelling narrative, comes out as the victor.
At the end of the day, the question is "what are you going to do about it?". Certain things just are because we're not doing anything about it. Doing about it is a ton of effort, might not be possible, might not worth it at all because the effort outweighs the results, might not worth it because the side effects are greater than the potential gains. Or maybe people care about other things. And because all of these concerns exist in all humans, those in power can exploit these too, in order to keep or further their power.
[0] https://en.wikipedia.org/wiki/Dark_triad
https://en.wikipedia.org/wiki/Social_stratification