Please answer a question about the following article about Alfred North Whitehead:

However, Mathews' frustration with Whitehead's books did not negatively affect his interest. In fact, there were numerous philosophers and theologians at Chicago's Divinity School that perceived the importance of what Whitehead was doing without fully grasping all of the details and implications. In 1927 they invited one of America's only Whitehead experts – Henry Nelson Wieman – to Chicago to give a lecture explaining Whitehead's thought. Wieman's lecture was so brilliant that he was promptly hired to the faculty and taught there for twenty years, and for at least thirty years afterward Chicago's Divinity School was closely associated with Whitehead's thought.

Who was frustrated in Whitehead's books but still interested?
Mathews