Why did the framers give the power to congress rather than to the states?

Congress has the power to issue currency because before that all the states had their own currency, which led to confusion and the devaluation of one state's currency within other states. 

The  ancient egyptians  who  built the pyramids  may have been  able  to move massive stone blocks across the desert by wetting the sand in front of a contraption  built  to pull the heavy objects