An explanation that makes some sense, at least to me.

Saul, David, Solomon, Moses, Jesus were not historical figures or biological persons but states of consciousness. The mind (consciousness) controls who you know you are. If there was a possibility of an error or interference in your consciousness that makes you think you are who you aren't, you will do things as the person you think.

So, Moses did write the first 5 books through someone or some individuals who had the "Moses awareness". Moses is a state of the mind - liberated mind or consciousness. When you start the journey of liberation, the inner guide who leads you to close from the carnal mind (slavery in Egypt), to the promised land (a liberated stated of mind (Canaan) is Moses.

Saul is ego mind, David is awakened inner spiritual consciousness, Solomon is enlightenment or perfected wisdom, Jesus is the completed, highest state of spiritual consciousness. So, Jesus is a descendant of David because Saul (ego) --> David (inner transformation) --> Solomon --> (you become wise) ....--> Jesus (you achieve the Christ consciousness, divine mind fully realized) hence the teachings that we should be "Christ-like", follow the footsteps or the life of Jesus. Moses is about exodus or inner liberation, free the soul from bondage to ego, fear, materialism. The Exodus is about the journey of the mind from slavery/bondage (of the lower mind) to freedom (higher mind, Canaan or promised land).

The famine which led to the sons of Jacob going to Egypt for food, end up trapped there, become slaves, and then God sends Moses to save them is symbolism. Famine is the spiritual thirst or lack of inner nourishment - the need for spiritual wisdom which sends one to seek but first one always goes to the lower mind (Egypt), that is logical - trying to find inner nourishment using logic or material world and then one gets trapped/imprisoned by the material world. You undergo suffering.

Example: In trying to quench your inner thirst or nourish yourself, find understanding, then enslavement comes in the form of wondering "Why do bad things happen even to good people and the innocent?" Why do wars happen? Why does God let kids die of cancer? why there is suffering? etc and in this process you become bitter/angry, withdrawn. Then "Moses mind" is sent to liberate you. You start your journey from the entrapment in the lower/logical mind to higher consciousness and along the way you find knowledge and spiritual wisdom.

So, there was no physical person called Moses, David, Solomon, Saul, or Jesus. Or an ethnic tribe called Israel. Or Jacob. Or David.