You shouldn't necessarily focus your research on the currently hot topic. Many people will flock to this area so you'll have considerable competition. And while today maybe you'll see many papers in area X being accepted to the big conferences this year, topics can get cold quickly and so will you.
But what about the other extreme, where you do research in an area of very small interest because you have a strong passion for it. Unless you get very lucky and this area goes hot in the future, you'll be giving up any chance of larger fame or fortune. But if you do good work in this area, you can use your passion to sell this area in a job talk and get strong letters from those few senior researchers in the field happy to promote people in their field. So often you can get a job at a reasonable university and spend your life working on what you love. Is that so bad?
Research always comes to passion and ability and you have love what you do and be good at it, no matter the topic. If you don't enjoy your research, you can usually make much more money doing something else you don't enjoy.