Devil worship naturally encourages doing harm to others for personal gain. Humans are competitive within hierarchies and there is always the motivation to do worse that others. This leads to a race to be the most evil.
In this way, members of cults and organizations that value doing harm to others, compete with normal-minded people for power in society. Devil worshippers have a competitive advantage, they are less restricted by morality. So it is natural for them to rise up in business and political hierarchies.
The higher they wish to go, the more immoral they must be. Then, at the top, the level of evil steadily rises as individuals compete to lead the increasingly established political class.
It is necessary to increasingly do harm in the world, in order to stay competitive.
Its not enough to sacrifice and consume humans, especially prepubescent children, in cannibalistic ritual ceremonies, and raping children, in order to gain supernatural powers. The perceived gain is too disappointing, and the ignorant conclusion follows that the gain was insufficient because the evil was insufficient. The killing must be increased, the power sought even greater. There must be ever increasing war, ever increasing killing, suffering. This naturally culminates in genocide. There is no greater confirmation of personal power than genocide. For those who seek personal power, it is the secret ultimate goal.
So there are times inhuman history where we see the rise of frequent war and genocide. This is the sign that the worst of the worst satan worshippers, the death cults, have cemented their hold on power.
Yet there never seems to be those who realize that being immoral and harming others doesn’t actually lead to any gain of supernatural powers at all. Only the illusion of power, from the fear or admiration of others, is gained, and their cooperation assured. When the numbers of these cooperators are large enough, then it is satisfactory compensation for the absence of supernatural powers. Power over more and more people then becomes the goal, and the ability to order others to kill on a large scale is a confirmation of achieving that sought after power.