It is not stupid and pointless. And this illustrate my philosophy in teaching, in which you learn new things on top of things you already know. That's why I wanted to ask you if you are already OK with gravitational potential energy, because if you are, then the electrostatic potential energy is no different other than mass being replaced by charge.
The BEST learning method is when, with some help, you discover for yourself the solution to the problem you face. I merely tried to guide you so that you can do this for yourself. Next time, when you encounter a problem, you will learn this technique of thinking where you try to see if there have been something similar that you've encountered before that can guide you to tackle the new problem.
Zz.