Of course it was DC's fault:
Significantly slowing down on the racing line at a curved section with heavy rain and very low visibility
Forget about racing, that kind of stupidity would also result in an accident in regular roads.
Later DC also realized this:
"The reality is that I lifted to let him pass me, but I lifted in heavy spray on the racing line. You should never do that. I would never do that now. In 1998, I didn't have the experience and the knowledge, and I had never had someone run into the back of me. And because someone pushes you, you react. So you act as though 'I didn't do that,'"
"The minute I knew he was there, and I was told by the team that he was and was trying to allow him to pass me, I should have made a smarter decision."
"The risk is that it could have been a very dangerous accident for Michael and Nurburgring could have been a very dangerous accident for me," he said....