The sheer man power they had. The allies had more troops than the axis powers could ever hope for. The US armies, Western Europe, and Russia combine was a huge force that the Axis had to deal with.
Key was inspired by the sight of a lone U.S. flag still flying over Fort McHenry at daybreak, as reflected in the now-famous words of the “Star-Spangled Banner”: “And the rocket's red glare, the bombs bursting in air, Gave proof through the night that our flag was still there.”
I think it was the past with Britain where only one person had complete power. This did not allow people to have a say, which was the reasons why the 13 colonies rebelled. Including the right of the people to revolt against a tyrannical government would protect the fundament of the united states government which was to give the people power and to make sure the US would not become something similar to Britain.
The articles of the Constitution explicitly outline:
B - a bicameral nation legislature.
Article I, Section 1 explains how Congress is split into the Senate and House of Representatives, a form of national bicameral legislature.
Because there had been many improvements made to succeed. Weaponry, generals, and tactics had changed. There was also more of a drive. The angrier the person,the more determined they are.
