You are quite correct about the Bush Doctrine of post- September 2001 until about early 2006 (only). From then on, the Bush Doctrine was slowly and irretrievably abandoned. North Korea then proceeded to do the same things they have been doing in the last 48 hours, under Bush's watch and in fact while he was in office. The result was further appeasement from the Bush White House and State Department. Behind the scenes, North Korea continued to build up both nuclear explosive technology (shown to the world day before yesterday) and missile trajectory power (demonstrated to the world on 5 April). These did not just all occur overnight, these were not technologies which magically kicked into force on 20 January 2009. Bush, and Clinton before him, clearly set the stage of danger to the USA from North Korea and which Obama, sap that he is, now inherits.
So you are correct in asserting the North Koreans would not try this with Bush in power. But by the same measure you are also incorrect, as it applies to his Second Administration, policies, and staff (namely Condi Rice and Chris Hill of State).