The elders at Ephesus knew he had acted faithfully, ethically, and morally. They knew that jealousy and lack of faith drove the attempts at discrediting Paul's ministry. They knew that people were seeking to have their influence over the people in the churches Paul had planted. And they knew that Paul wouldn't be there to defend the true faith - though he would write letters to the Ephesians, Philippians, Colossians and to Philemon from his Roman prison. Still yet his going was a loss.
But even as we consider powerful missionaries or much-loved pastors leaving beloved people, we must also remember that graveyards are full of indispensable people. There will be others to carry on the mission and keep the church moving forward.