I think he's simply a careerist elitist
Here is an article about David Frum's website The New Majority, and his "new conservatism," by American Thinker writer J. R. Dunn.
The article distinguishes between the American and Canadian character, which I think is correct, and discusses how Frum’s Canadianness obstructs his view on American conservatism. But, I don't think that is how Frum sees things.
I think that Frum, like many conservatives in the U.S. and Canada, and probably in Europe too, is just sliding ever closer to the liberal state of mind. But I don't think he was a genuine conservative to start with.
Frum in a CBC interview of him soon after his book Comeback Conservatism that Can Win Again came out in 2008, talks about a new type of conservatism. He says the following in the interview:
We're moving toward new formations, not conservatism as we've known it, and not liberalism either... and there are going to be big prizes for the people who can figure out how to get there first.So, these new "formations" are neither conservative nor liberal, and in fact the compensation for those that come up with this new movement is...big prizes.
I think Frum is actually a careerist, and an elitist. That together with his liberalism, which shows its face regularly, makes him unable to accept true conservatism. I remember reading somewhere that he thinks conservatives should reconsider homosexual marriage. That was about the time when I stopped taking him seriously.
But, what about the elitist part? Dunn is correct in saying that Frum doesn't relate to ordinary Americans, and uses Sarah Palin as the example. I don't think Frum dislikes Palin because she represents the "Yanks [who] are simply a louder and more rash version of anybody you’d find above the 49th," nor is it for any principled reason relating to her tenuous conservative positions, but simply because he is an elitist. I think it is the same reason he dislikes Rush Limbaugh.
Frum recently wrote in the National Post:
[We] are afraid that Palin's distinctive combination of sex appeal, self-pity, and cultural resentment has a following in today's GOP.Nothing about Sarah’s ideas or positions on conservatism; all about the superficial Palin effect.
Elitism, these days, I think is a liberal trait. Those loud and raucous conservatives, wherever they may be, need the civilizing presence of elitist careerists liberals like Frum. Of course, in Canada, one will be hard pressed to find such raucous conservatives, and it is these elitist liberal Canadians who want to teach those conservative Americans a lesson or two on decorum.
So Frum’s talent might be most beneficial south of the 49th, where there are more of those rambunctious conservatives to civilize. In fact, he is now an American citizen – after a long American residency. With his new website, and his quest for a new movement, he is setting the stage for a new and prosperous career.
Frum isn’t really inventing anything new, or corrupting Americans with the passivity and liberalism of his native Canada. I think he’s just gauging the direction of the wind to make sure that he is as relevant today as he was yesterday. In that regard, he might be one less Canadian Americans can do with.