So, what’s a neocon? Irving Crystal, largely regarded as the founder of the ideology, explains it best:
http://www.weeklystandard.com/Content/Public/Articles/000/000/003/000tzmlw.asp
Woops, it's Irving Kristol. What's wrong with my spelling today?
IMHO, neoconservatives are a subset of the conservative movement which had its roots in the foreign policy of Scoop Jackson. Jackson, a Senator from Washington State and Boeing, advocated a muscular foreign policy which in the Cold War found allies among his conservative Republican colleagues. He also fought hard to permit Jewish emigration from the Soviet Union. As a Democrat, however, Jackson frequently parted company with conservatives and their desire to keep the size and scope of government in check. The Democratic Party's aversion to the military and ennui towards the Cold War made the move to the conservative Republican Party under Ronald Reagan more palatable to neocons assuming they were willing to look the other way or ignore Reagan's support for lower taxes, the 2nd Amendment, states rights, etc. As a result many wound up in the Reagan Administration and Republican Party.
The Bush administration, staffed to an extraordinary degree by AEI (the primary neocon think tank) at the Pentagon and more than willing to expand domestic spending in virtually every direction must have seemed like a dream come true from their point of view.