Complex sentence: In 2035, Lunar Industries have made a fortune after an oil crisis, by building "Sarang", an automated lunar facility to mine the alternative fuel helium-3, which is used primarily to power fusion reactors and other things that run on fusion energy.
Split into simpler sentences: In 2035, Lunar Industries have made a fortune after an oil crisis by building "Sarang", an automated lunar facility to mine the alternative fuel helium-3. Helium-3 is used primarily to power fusion reactors and other things that run on fusion energy.