Dark energy and matter are not explanations. They're the names given to the problems of discrepancies between model and measurements.
More explicitly, they are names given to a proposed solution to the problem of discrepancies between models and measurements. Measurements show that objects in the universe move in a way that isn't fully accounted for by the gravity of all the things that we can see (that is, the stuff emitting or reflecting light), so the proposed explanation is that the discrepancy in motion is due to the gravity of things that isn't emitting or reflecting light.
This is a hypothesis. It fits the facts we have so far. We still have to find evidence that the hypothesis is correct, or that the hypothesis is wrong. That's how science is done. You come up with a hypothesis that fits the measurements you have, then you look for ways to see if the hypothesis is correct.