There are a lot more "fads" than that in science. They're also more often called "hot topics." But, it's often because someone or some group has made a major breakthrough in a topic that suddenly makes it popular or possible for others to jump on it. The field of research is not necessarily a new one, it just gains rapid popularity, a lot of funding is put into it, progress is made, then a new "hot topic" comes along.
I would actually argue this is a good method of doing and funding science. If a lot of funds, groups and resources are focused on a particular topic at the same time, more progress can be made quickly than if people are dabbling with it here and there. When new progress runs out of steam, it's time to turn to another subject.