Weren't the crew already doomed before WAU

[Abion47]

The WAU created the Vivarium long before it went berserk. It was a continuous process that started when the comet hit that made the WAU's protocols begin to overwrite itself. What it did in the beginning isn't clear, but at some point that involved creating the Vivarium, which people found and Catherine used to create the Ark. Some time later, the WAU went a step further and started corrupting, capturing, and killing people.

So, yes, the WAU succeeded in its task. And then it took a few steps backward.