Why did delegates write the U. S. Constitution?

Troubles with the existing Confederation of States finally convinced the Continental Congress, in February 1787, to call for a convention of delegates to meet in May in Philadelphia "to devise such further provisions as shall appear to them necessary to render the constitution of the Federal Government adequate to the Union.

troubles with the existing 'confederation of states', as it was called, made the delegates join together to replace the articles of confederation with something better, resulting i the creation of the US constitution.