Why do people seek to be leaders? Their basic motivation will have a significant effect.
The basic benefit of leading is that it allows you to set the direction and recruit others to your cause, thus achieving far more than you could alone.
Leaders may well have grand visions of very different futures in which the world is changed in some way (presumably for the better). If they can communicate that vision to others, effectively 'infecting' them with the idea, then this will create a sustaining motivational force in others towards a common goal.
A basic need is for a sense of control, which may be gained either by ceding control to trusted others or by taking control and acting yourself. Leaders use both sides of this, seeking to be in charge and also being the person to which others cede control of their actions.
A common motivation is seeking after power, which McClelland's Acquired Needs Theory identifies as a basic need. Power is the ability to achieve your goals. Gaining power thus allows the leader to achieve a wide range of other things.
Power can have the effect of a drug, and even leaders who did not originally seek it can find its effects intoxicating and end up seeking it for its own sake. Thus 'Power corrupts, and absolute power corrupts absolutely.'
We all have some balance of concern for ourselves vs. others, where we seek both to achieve personal goals and also seek to altruistically help others. Leaders also may be motivated some combination of the desire to serve themselves and to serve others, which may range from extreme positions to some intermediate balance.
Musser (1987) looked at charismatic leaders and identified that they not only seek to connect people with idealistic goals, but that they often also seek to instill devotion of themselves by their followers. This, as other preferences, is a spectrum on which people have preferred positions.
Thus it is possible to have charismatic leaders who are highly altruistic. They may also be very narcissistic, seeking leadership primarily for the admiration and worship that they may gain.
Narcissistic leaders tend to surround themselves with sycophantic and loyal subordinates whose main role is to stroke the ego of their leader. Truth, particularly when it is critical of the leader, thus tends to be hidden, leading to failure, cover-ups and an eventual descent into collapse. This is exacerbated by the leader's belief in the superiority of their own capabilities which results in them in making autonomous and risky grand decisions with limited information.
In an altruistic leader, the primary purpose is to help others and make a difference in the world. They may be charismatic or quiet, dominating or reticent in style, but their goal is still to act for a purpose outside of themselves.
The altruistic leader may well have a close alignment of identity with the target group or purpose, and hence may be accused still of being self-centered. The difference, however, is in what they achieve for others.