Why people do feel insecure in job even if they are talented & most suited for the job? Is it because they lack confidence or are they afraid the other factors?

Accordingly to me ability needs opportunity. Just being talented isn't enough. You should also have platform to perform. People to afraid of the loosing that platform. However, sense of insecurity is always in ones mind. No necessary that your hardword, talent and loyalty will be recoganized in same way. So, people do afraid of these OTHER factors.