Why is it important to have three branches of government?

So there is no one person who is too powerful in the government.

Explanation:

The US was formed after the colonial leaders agreed that King George III was a tyrant, and they wanted a say in their own government.  Once they won the revolution, many feared that they would end up with another absolute ruler like many European countries had at the time.  The original government, the Articles of Confederation, show this fear as there was no strong federal government or leader.  This didn't work out so the founding fathers created the Constitution which split the government between those who make the laws (legislative branch), approves and carrys out the laws (executive branch) and decide whether the laws are Constitutional (judicial branch).  With this set up, no one person can become an absolute ruler or dictator.  

it affected it because the kingdoms (with trade) slowly got richer and richer.