You're assigning a degree of competence to McCain he doesn't actually possess. The only thing he's qualified for is holding down a government sinecure and posturing. When he's led any kind of successful legislative push, it's inevitably a cave to liberal interests. He's just an incompetent.
Dubya was incompetent, but less incompetent than McCain. Think about how Dubya almost lost to a couple of stiffs (Gore and Kerry). How could anyone think that a loser like McCain could defeat one of the greatest political talents since FDR - someone who secured the some of biggest popular vote margins ever in % terms, made huge strides in the liberal agenda despite GOP legislative majorities in 6 of his 8 years and emerged at the end of his tenure with a net positive poll rating? It's pretty amazing that the 2008 GOP primaries came down to two stiffs, Romney and McCain, both political zombies. When it got to that point, the writing was on the wall - even Hillary would probably have beaten either of them.
I think you gravely underestimate these individuals. McQueeg, Willard, Shrub, Zero, Hillary... they’re all a part of the same corrupt Deep State Combine. The fact that many of us didn’t wake up to that fact a long time ago is astonishing. The writing on the wall was about as glaring as could be. Why do you think they all react the same way and use the same talking points against President Trump ?