Why did george grenville believe that the colonists would readily accept the stamp act?

George Grenville, the British PM at the enactment of the Stamp Act, instigated the measure with the aim of raising money to cater for the large standing army in the colonies after the end of the French-Indian war in 1763. He was eager to raise revenue "by means the most easy and least objectionable to the Colonies." As such, he underestimated colonial opposition to the tax by believing that the Stamp Act was the easiest and least objectionable to the colonies. This was informed by the belief that the colonies required the large standing army left behind by the French-Indian war.