From what I can tell, Bush failed to win over New Jersey independents and moderates. Also Bill Clinton was still a popular president.
This, people liked Bill Clinton and a lot of voters at the time didn't think there was much difference between the two so suburban voters stayed put for gore.
http://www.cbsnews.com/campaign2000results/state/poll_njop-.html
Gore won across all income groups and even 1/4th of conservative voters in the state.
In 2004 it was pretty different because 9/11 made a lot of potential bush voters who stayed out because of the good economy in 2000 to turn out in New Jersey.
Weird in those polls that Bush did better with Catholics than with Protestants...
