The culture of Thessalonica did not make it easy for new believers to grow in faith. It was hostile to Paul and anyone associated with him because what he taught challenged the way of tolerance for worshiping whatever god people wanted to worship.
Paul got run out of town before he could establish leaders and teachers, so he worried about the young church and prayed for it with longing and trepidation for what the culture might to to it.
He finally sent Timothy to check on them, and learned that they were not only standing strong against the culture, but they were living out their faith with love for each other. They were eager for Paul to return and continue to teach them.

So, the title of this post is tongue in cheek, but I suspect any pastor would be excited to teach a congregation like the Thessalonians. They heard the Word, responded in faith, and then lived out what they believed in spite of a culture that despised them.
As a teacher, I understand why Paul was so excited to return and continue teaching. It is fun to teach people who want to learn, and joy comes when students actually practice what they’ve been taught.
Many pastors face congregations that are apathetic or demanding or in church for the social hour. That has to be discouraging and demoralizing. However, an enthusiastic congregation that is excited to hear the Word and then live it out must be invigorating for the preachers.
Paul ends this chapter with a benediction that would be a powerful prayer for churches today: May the Lord make you increase and abound in love for one another…so that he may establish your hearts blameless in holiness before our God and Father.