He has a massive ego, and is convinced he knows best. He's already said that if he couldn't have used the excuse of the claim of WMD to invade Iraq, he'd have found another way of removing Saddam. So he's admitted that he wanted regime change all along (and he lied to the British Parliament when he said that wasn't his aim), although that was clearly against international law.
Here, for instance, is an article about his attitude to Kosovo:
http://news.bbc.co.uk/1/hi/325989.stm . And his (laughable, if the subject weren't so serious) attempts at being a 'peace envoy' and trying to 'bring all faiths together' show he still believes he's a 'great' international figure.
Blair wanted a way to depose Saddam. He found WMD a conveninent way to do it, and, as the Downing Street Memo said, 'fixed the facts around the policy'. The evidence so far to the Chilcot Inquiry has clearly shown that people were working that way round. Goldsmith was looking for ways to legitimise an invasion. In 2003, he wouldn't talk to the French negotiators about resolution 1441, because that would have weakened the case. But he was happy to talk to the American negotiators, because that gave him a claim that 1441 meant no further UN decision was necessary.