How to answer “Why choose us” in a job interview

Same as many people, this is one of the questions that gives me the headache when preparing for a job interview. Until recently, I was lucky enough to work with a human resource consulting business, and I would like to share why businesses ask this, what they are looking for, and how you should prepare for this question.
Why
Businesses are always looking for a candidate that stands out. They want someone that is excellent, fit for the position, and most importantly, fit for their organisational culture (will discuss later). In other words, they want you to be right for them, they also want to be right for you. Therefore, you can be more satisfied for the job, you work better, and you stay for longer.
What
This question can also be used to test you commitment though seeing how much research you have done about the business. It also tests your ability to research and comprehend the business’s structure and goals, so you are capable of working under the business’s framework and future vision.
How
You need to have a through understanding to the business’s culture. There are 3 specific things you need to research about. These are big tips as consulting businesses construct organisational cultures for other companies basing on these 3 components.
Employee
Find out what characters the employees show, do they value innovation, flexibility, or pragmatism etc. note many characters can co-exist. Find out how they develop their employee’s skills. This is also valuable information for you to know if the company aims to develop appropriate skills for your own growth.
Organisational structure
Find out what the business does. What are the business units, and their contribution to the total profit. How many employees does the business have? What’s the business’s most famous product? How much is invested in research and development and marketing each year? The list could go on forever. Just make sure you build a general model of the business’s operations and research more to add details for your understanding.
Leadership
Research the autobiography of the CEO of the business, find talks he/she has made. Since they are the persons responsible for the general vision and most influential component of the organisational culture, an understanding to the character of the leader could really give you the grasp of the general organisational culture and visions of the company.