Yeah, because I agree with Bush on a number of key issues as well, in fact, probably most (but certainly not all) of the same ones that McCain agrees with him on. I also disagree with Bush (and McCain) on certain issues.
However, at the end of the day, I agree with McCain's stated position on most issues far more than I agree with the stated positions of Obama. How much my positions, or McCain's positions, or even Obama's sync up with Bush's positions is irrelevant. Now how many of McCain's positions survive his first 100 days as president is a concern....but wouldn't even have that much comfort with Obama.