The Nobel Peace Prize has become increasingly an expression of political and social opinion rather than a recognition of achievement. So, it likely is not taken as seriously as it was in the past. However, the choice of the President, which apparently has been made purely and indeed expressly because of a feeling, and a kind of hope, makes one wonder just what the Nobels mean, anymore, outside perhaps of the sciences and medicine.
The fact that reaction to the award has generally been described as "stunned" is significant. Relatively few appear to believe the President deserves the award, at this time (I expect efforts at justification of the award will be forthcoming). So, it seems pointless to debate whether it was appropriately given. If it is to be awarded based on remarkable achievement in the cause of peace, then it seems apparent that the choice, this time, is inappropriate.
More interesting to me, I confess, is the effect to be anticipated. The President is already very well received in Europe, so the Prize cannot be said to do him a great deal of good there. I doubt it will do him much good in the country over which he presides. I suspect this will simply give greater weight to the view that he is of little or no weight, and that those who applaud him do so for no legitimate reason. And, it will make him appear to be less worthy if he fails to accomplish what he, and others, apparently believe should be accomplished on his watch. Those who award the prize may have thought to do him a favor, but ultimately I think they have merely encouraged his enemies, and increased his burden.