The Vulture article delves deep into the potential whys. It appears he suffered serious abuse by his parents who were very prominent Scientologists, pretty much the leaders of the cult in the UK.
Then, as an adult, he refused any kind of therapy. Instead, he became an abuser himself, even going so far as to potentially traumatize his own son.
None of that excuses his behaviour. He's obviously very intelligent and his works show that he knew very well that what he did was evil and inexcusable. He wrote a chapter of Sandman about this exact thing! But in the end he just didn't care. Because he probably thinks he's rich, he's famous and the rules don't apply to him.
I agree, not just because I enjoyed the show, but it seemed like it was a fantastic opportunity for many of the people that worked on it. Gaiman's shit behavior shouldn't spoil the hard work of the hundreds of people involved in the show.
They already cancelled its spinoff show Dead Boy Detectives. And from what I understand, Gaiman was pretty closely involved in the production of Sandman, so continuing the show without him probably wouldn't be so simple. I'd say, just assume it's dead and done now and save yourself the disappointment later.