He doesn’t love presidential power, he respects the Constitution.
There’s a talking point already circulating through the media: Brett Kavanaugh not only “is devoted to the presidency,” he may well have been selected to protect Donald Trump. Here’s Vox’s Ezra Klein voicing an almost conspiracy-theory level idea about Kavanaugh:

As you can see, the basis for this belief is a 2009 Minnesota Law Review article where Kavanaugh argues, based in part on his own experience working with Ken Starr as he investigated President Clinton, that “the nation certainly would have been better off if President Clinton could have focused on Osama bin Laden without being distracted by the Paula Jones sexual harassment case and its criminal investigation offshoots.”

And what’s his proposed remedy? He suggested not that judges block investigations of the president but instead that Congress “consider a law exempting a President — while in office — from criminal prosecution and investigation.” He makes this proposal in the same law-review article, by the way, where he also suggests that Congress should assert greater authority over war powers, and he floats the idea of a single, six-year term for the president (an interesting idea, by the way.)