One of the most important things a leader can do is to define reality as it is, rather than how people want it to be.
This does not mean mindless disclosure - Churchill told the British people that they were in peril but he did not reveal just how bad things really were lest that encourage the enemy - but it does mean large amounts of candor. It requires a clear eye of what's working and what isn't as well as a grasp of where the organization must go and how it should proceed.
Organizations, like individuals, are prone to daydreams, miscalculations, and inertia so the leader can expect resistance. This may be so even when the need for change is howling and clawing at the door. It is safe to assume that nothing is obvious and that core values will require periodic boosts. In order to gain support at all levels, the leader must be able to persuade.
The homework needed for a persuasive argument will involve anticipating the counter-arguments in order to spot valid objections and overcome the weak ones. The valid objections, of course, should be accommodated and the weak ones dissected so their negatives can be easily understood. Just ramming through various changes is a major mistake because it embraces narrow analysis, ignores substantive objections, and fosters resentment.
"Because" is a popular explanation by parents but it certainly needs far more elaboration with adults, especially since a lethargic acceptance of the way things have always been handled is often popular. Defining reality is a key prerequisite for positive change.