Every once in a while, Mr. Frum is a talking head on the Canadian news channels. I’ve always found him to be well-thought on his positions — even when I do not agree with him.
I took a look at his Wikipedia article. From the books he has written, he has been on the wrong side of recent history on a few occasions. And he seems to have made a good living with his conservatism.
As far as his responsibility for the rise of Mr. Trump, I would say that he bears no more or less responsibility than the rest of the American media. Mr. Trump was a good sideshow to bring in advertising dollars. He still is a good sideshow.