Trump didn't win by a slim margin at all, he lost the popular vote, but only largely because of California. He had early calls in several states that Hillary was supposed to win. Hillary lost states she never stepped foot in, she was just not a strong candidate, she didn't campaign, she had little ground game and conceded states simply because they were a "firewall." Trump should have never been within spitting distance of any Democratic candidate, especially after Obama who was fairly popular among moderates.

Trump may have won on a slim margin, but he was supposed to lose on a huge one, by most predictions. If CA merely granted a net positive, then it likely paled in comparison to whatever else substantially affected results.