I understand about May. President's don't have to be obnoxious to succeed. Eisenhower and Reagan certainly weren't. Both were highly successful. I suppose depending on what side of the fence on stands whether one would look at Obama as being successful or not. But he was tactful and well liked as a person. Usually between 5-10 points higher on the likability scale than on the approval rating.
It's Trump's uncouth, name calling persona that is holding him back. If one goes inside the polls one finds out on the policy and issue level, those for and against are fairly evenly split. Yet he is always ten points or so below where he should be on job approval. "Perhaps this will help. Trump Approval Lower Than U.S. Mood Might Predict"
Trump Approval Lower Than U.S. Mood Might Predict
Put it this way, a friend of mine when talking about Trump's character, personality, he said that he could agree with him 100% on the issues and policies, but he still wouldn't vote for him.