https://en.m.wikipedia.org/wiki/Nuclear_fusion
The fusion of light elements up to a certain nucleus size releases energy. However, fusion only occurs at very high temperatures and pressures. The goal is to 1) create the conditions for nuclear fusion (which they did), 2) have the fusion reaction produce energy that sustains those conditions (they did for 48 seconds), and ideally a tiny bit more, 3) gather residual energy that isn't critical to the reaction itself, which is the part that looks like a steam engine.
Playing the base solo campaign in SWtOR and actually listening to the dialogue and following the story with each class I think gives a similar feeling (so long as you skip the non-story quests). Star Wars IP can be good.