Paul launches, in verses 6 and following, immediately into a rebuke of the Galatians for their foolishness in listening to the agitators. In other words, Paul is signaling by his lack of any thanksgiving at the introduction of the letter that he views the situation of the Galatians as a very, very serious one, and he wants to get right to business by lambasting these agitators for the message they’re bringing—the other gospel, which Paul says is, in reality, not a gospel at all—helping the Galatians