If Galatians was written as Paul packed for this meeting (metaphorically - I realise he didn't have much to pack!), it could explain the almost complete lack of personal information in the letter.And Michael Pahl echoes:
Paul is uncertain how the council will go, uncertain how the "pillars" will respond given Peter's and James' apparent reneging on their prior affirmation of Paul's gospel. He is uncertain how the Galatians will respond, uncertain about this whole region he has just recently poured his life and energies into. Paul is certain about his call and his gospel revelation, but he's uncertain about almost everything else related to his personal "mission."Other than the things already mentioned, I find this suggested scenario implausible given the direct analogy that Romans provides. In that epistle, Paul is about to set off for Jerusalem (15.25-26), and he is anxious about how he will be received (15.30-2), and he has plenty of time to make advanced travel plans. On balance, an alleged Pauline journey to Jerusalem to take place just after the writing of Galatians is not fully persuasive as an explanation for the lack of travel plans in the epistle.
Richard Fellows, also in comments, makes the following suggestion concerning Paul's success in Galatia:
I don't think we can know for sure whether Galatians was successful. The survival of the letter may suggest that it was. It seems that the readers respected the letter sufficiently to preserve it.For Jimmy Dunn, this is a decisive point in favour of the success of the epistle – it was saved by the Galatians and so it achieved its purpose of persuading them of the proper course of action. Even J. Louis Martyn, who is somewhat less positive about the letter’s success overall, still feels that the existence of the letter provides us with decisive evidence that at least some of the members of the community must have been won over. However, the fact of the existence of the letter tells us nothing about its success or otherwise. It takes only one person to save an epistle, and one person in several churches is some way from success. (And there is only one recipient of Philemon, and that one survived, a letter somewhat less important or impressive than Galatians). But more importantly, both Harry Gamble and David Trobisch have made persuasive cases that Paul himself would have kept copies of his own letters, that he was, effectively, the owner of the first Pauline corpus. A moment's consideration confirms the plausibility of this scenario. You do not go to the trouble of writing letters wrenched from your heart only to trust them to the vagaries of travel, loss, fire, theft, the elements.
The question is, in fact, not why any recipients troubled themselves to save the epistle, but rather whether Paul or his associates would have had any reason to destroy the epistle. Here we enter the realm of the imagination, but I can think of several good reasons why Paul and his companions would have wanted to save this letter for posterity. (a) For Paul himself it provided a useful rough draft for his epistle to the Romans. Of course he does not know that at the time of writing, but perhaps he came to think that there were arguments in Galatians that he could (even should) revise, refine, rework at a later point. The loss of Galatia causes him to think again about key elements in the argument of the epistle, and in the issue his opponents there had spotlighted. (b) For his followers and the earliest collectors and keepers of his letters, the only important thing would have been that Paul himself had written this letter. (c) Though he had lost, Paul no doubt felt that he was still right – he had a basic pride in his argument – and for this reason he and his followers save the letter. It is rather poignant that the letter itself survives long after the communities that rejected it and its writer, so that ultimately it did find its own kind of success, canonised and remembered and in the end able to persuade later generations who had no access to the other side of the argument.