What sorts of things could cause a person to have so many fears?

One usually can trace back the causes and effects with a good therapist and a good attitude.

We are formed young and by our relationships with our parents…good, bad or indifferent. The early programming is really hard-wired and takes a lot of work to 1) understand and 2) work around or change, to a small degree.

I agree with @gailcalled We experience so much throughout our childhood and it impacts us, whether or not we are aware of it at the time(most often not). That’s where exploring these fears with a therapist is really beneficial in getting to the root cause of the fear.
Fear is like any other projection, but it takes a lot of work to discover what’s at the core of it.

Therapy is your answer.

I think fears are the consequences of our life experiences. I agree that many or perhaps most are based in childhood but I don’t believe they stop. I have had experiences as an adult that produced fears in me. Not all fear is a bad thing, fear of walking in front of a moving car saves your life. Fear of living with an abusive partner is also a good fear. Fears which cause you to be incapable of doing the things in life that you want to do are usually bad. Irrational fears are a waste of time, but none the less scary.

Counseling is good to help you separate and catagorize your fears and deal with the ones that are hampering you.

In my experience they can arise from a single traumatic incident or via slowly learned thought processes that tell you that making mistakes can have dire consequences.