a) they came unprepared and
b) their personality did not fit the culture of the company
Understanding the company culture and how you might be a great fit is vital during an interview, so make sure to do your homework. You can even look up people who work at the company; what kind of work and education background they come from? Learn more about your potential, future co-workers. You can get a good general idea about the company culture about the kind of people that work there. Ask your network and friends about the company, they might know someone who works there or have worked there themselves.
Some things you should consider when it comes to company culture:
- Does it fit my personality?
- Am i going to be happy in this kind of culture?
- Do I see myself staying with this company and growing?
- Does this company/job fit my personal life and my future goals?
The worst thing you can do is pretend to be someone you are not. Many people have two personalities; one they have for work and one they have once they leave work. Eventually they get burned out and end up breaking down in either their personal life or professional. Now, i don't mean you should show up at your job and play hard rock in your office and get too comfortable. But, you should be happy in the company and can be yourself and enjoy your co-workers and the work that you do. We spend more time at work then with our families and doing anything else, so make sure you are happy at your work. At the end, you don't want to look back and realize you spent all this time away from your family at a job that made you miserable. For example, don't go into the corporate world if you don't enjoy it. Don't join a start up if you don't like challenges and surprises in your work. Do your homework. Do informational interviews to learn more about the company you are interested in, it might not be what you expect it to be or it might reassure your interest. It is better to find out before you sign that contract. Informational interviews are also great for networking.
You can read more about informational interviews here: http://www.forbes.com/sites/jacquelynsmith/2013/12/11/how-to-land-and-ace-an-informational-interview/