Why were some delegates opposed to having a president to lead the executive branch

Some delegates were opposed to having a president leading the executive branch because there could generally only be one president in a nation, and the delegates feared this one person would try to take over the other two branches of government leading to a state of government in which one rules over all.

false, the two are unrelated

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.