The context was he wished we done it right the first time.
He does not go on to start speaking against it later, in fact in 2003 he actually praised the attack.
Later in the year he said things about, he would fight terrorism just as hard alluding to the fact that he would attack a country just not necessarily Iraq, but then by December of 2003 he stated that we had to go in to find Sadam which he was clearly in favor of, he repeated, we had to find him, even while mentioning people started questioning US being in Iraq. Didn't really mention he opposed the actual going in but just said there was talk of opposition.
My main point being that Trump lies about being completely opposed. Him saying he made headlines being opposed are lies. Trump did mention in 2004 he would have done it differently, thats all.