Why was Paul thankful?
First, I thank my God through Jesus Christ for all of you, because your faith is proclaimed in all the world. (Romans 1:8 ESV; see also 1 Corinthians 1:4; Ephesians 1:16; Philippians 1:3; Colossians 1:3; 1 Thessalonians 1:2; 2 Thessalonians 1:3; Philemon 1:4)
Greet Prisca and Aquila, my fellow workers in Christ Jesus, who risked their necks for my life, to whom not only I give thanks but all the churches of the Gentiles give thanks as well. (Romans 16:3-4 ESV)
I thank God that I baptized none of you except Crispus and Gaius, so that no one may say that you were baptized in my name. (1 Corinthians 1:14-15 ESV)
I thank God that I speak in tongues more than all of you. (1 Corinthians 14:18 ESV)
And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers. (1 Thessalonians 2:13 ESV)