What events led the new nation to write the constitution?

A variety of reasons. The ongoing debate about federal power had tipped to the side of the 'Federalists,' for one thing. But also, and perhaps more importantly, the practical experience of the nation during the War for Independence had demonstrated that, without a stronger federal government, it would risk failing in its 'grand experiment' of republican self-governance.

geography

this is because warmer climates often don't get people sick from the flu and regions where it was often colder more people received the flu. hope this if you need more reasoning i am here to