The primal drives are greed, hatred and delusion, being the necessary motivations for survival in the physical world, for obtaining and protecting food, shelter etc. The arahant is able to overcome the primal drives. Fear arises basically from delusion about situations, and fear of the suffering (dukkha) which is inherent in the world.
the world is shrouded.
Because of stinginess,
it doesn’t shine.
it’s smeared — I tell you.
its great danger & fear.”—Sn 5.1
So fear arises in the ordinary person in response to dukkha and the lack of any knowledge of it, or how to overcome it. Therefore the removal of fear is achieved by the gradual removal of ignorance. In MN 4, the Buddha points out that ascetics who resort to wilderness abodes and experience fear, do so because of lack of sila. Sila gives rise to tranquillity. He also says they are “drooling idiots”, that is they have not developed discernment (insight).
Fear arises from attachment and so is common in the ordinary uninstructed person, this is why it doesn’t feature in the suttas, but is more often mentioned in the Dhammapada (188-192, 216, 317, 351). Logically as the practitioner approaches stream-entry fear diminishes.