There had been an amendment process in the Articles of Confederation. It required that all states agree to an amendment. Rhode Island famously blocked adoption of an amendment to give Congress power to levy tariffs, and the result was the Philadelphia Convention (in which Rhode Island, note, opted not to participate).
The amendment process only seems difficult if one approaches it from the perspective of one who wants amendment to be easier than now. If one approached it from the perspective of, say, James Madison, Alexander Hamilton, Robert Morris, James Wilson, or someone else who had wanted to give Congress a tariff power under the Articles, today’s amendment process–which has been used successfully 27 times–seems much easier.
No, there’s no evidence for that last idea. In fact, it’s contrary to what the Federalists in several states told their state electorates and ratification conventions: that the Constitution meant what it said and warnings the Federal Government would grab more power were unfounded.