In the 1770s, the chief aim of those who wrote the new state constitutions
was to

Prevent state governments from becoming tyrannical

Explanation:

The framers of the constitution learned from the mistakes that the British made when designing their government system. When the government is given with too much power, it will risk the government abusing their power covert the people for personal gain.

This is why the constitution created several failsafe to ensure that the governments won't turn into tyranny. As an example, the framers mentioned that the governments consist of the people who are elected by the citizens to represent interest. If the citizens feel that the official is underperforming , they cold easily vote him out.

yes it is important for the three govenrment bodies to work independently as by this the can do better for development and welfare of their country

Hope this will help you