The First Hundred Days Are For Listening, Not For Proving
The pressure to demonstrate value early produces changes that later have to be unwound.
A new chief executive arrives carrying a debt of legitimacy. Nobody yet has evidence that the appointment was right, and the temptation is to manufacture that evidence quickly by changing something visible. Restructures are popular because they are unambiguous, fast and entirely within your gift. They are also the change most likely to be made on the least information, because you have not yet had time to learn which of the odd arrangements you inherited are dysfunction and which are load bearing.
A better use of the early period is systematic conversation. Talk to every person who reports to you, and a deliberately chosen sample of people three levels down, and a set of customers, funders or members who have no reason to flatter you. Ask what is being avoided, what everyone knows and nobody says, and what they expect you to change first. Write the answers down and look for the things that are said by people who do not speak to each other. Those are the real conditions.
Resist the urge to promise during these conversations. People will present you with problems that have a satisfying, immediate answer, and giving it will feel like leadership. It is mostly the accumulation of commitments you will not remember and they will. Take the input, say clearly when you will respond, and then actually respond. The competence being demonstrated in the first period is not decisiveness. It is the far rarer one of following through on small undertakings, which is the only foundation on which the large ones will later be believed.