The framers of the constitution worried about a president that would have too much power. One of the reasons why some framers (who were usually anti-federalists) were worried about this was because of their experience with Great Britain. When they were colonists, having a ruler that had too much power (King George III) eventually lead to the American Revolution.
On the other hand, other individuals (federalists) wanted a strong president because of their failures with the Articles of Confederation. The Articles of Confederation was America's first constitution. This constitution did not have a president. This caused several problems, as there was no one individual to turn to in a time of crisis.
Eventually, the constitution implements a system of checks and balances to make sure that the executive branch (aka the President) has their power checked by Congress and the Supreme Court.
