The reason the founding fathers chose ratification by popularly elected state conventions in ¾ of the states to ratify the US Constitution was:

The chances of getting approval from the state legislatures was not sure, it was also believed that approval by the people of the would have a better constitutional and moral backing/support.

Explanation:

Ratification by people is a process usually adopted by government or political leaders in order to get the popular support of the people, it is known to have a stronger legal and moral authority, as it is believed that the power belongs to the people.

THIS PROCESS OF GETTING THE APPROVAL OF THE POPULARLY ELECTED STATE CONVENTION WAS ACTUALLY CALLED FOR IN ARTICLE VII OF THE CONSTITUTION.

he was able to speed up production of the processing of seeds

immigrants from northern and western europe continued coming as they had for three centuries, but in decreasing numbers