According to Equiano's account below, why did many slaves die?

"The closeness of the place, and the heat of the climate, added to the number in the ship, which was so crowded that each had scarcely room to turn himself, almost suffocated us. This produced copious perspirations, so that the air soon became unfit for respiration, from a variety of loathsome smells, and brought on a sickness
among the slaves, of which many died." -Olaudah Equiano, The Interesting Narrative of the Life of Olaudah Equiano, or Gustavus Vassa,
the African, 1789

They were killed in mutiny attempts.

They were beaten to death.

They could not breath due to overcrowding.

They could not breathe due to overcrowding, which led to sickness and death.