Building a career does not happen overnight. A career is cultivated over time, built through education, training, and experience. Your career is also influenced by your successes, failures, side-steps, stops, and renewals.
The interviewer asks: Why has it taken you so long to find a job?
It’s difficult to believe that employers are still asking this type of question. Don’t they read the newspapers or listen to the news? If they were informed, they would know the answer; i.e. jobs are very scarce and difficult to find these days, and unemployment is still high, despite improvements in the economic picture.