After reading this answer, I wondered the title question. It seems part of our difficulty in harnessing fusion power is controlling the hydrogen and helium (plasma?) while fusion is taking place, i.e. using electromagnetic fields.
So I wondered, might it be easier, from an engineering standpoint, to control and harness the power of fusion of heavier elements?
The more protons the target nucleus contains, the stronger becomes the electrostatic repulsion between the target and the fusion "projectile" (typically a helium nucleus, 2 protons stuck together with 2 neutrons).
This means it takes more work to crush them close enough together to stick. This can be thought of as an "activation energy" barrier which must be overcome before the fusion reaction can occur. The net energy release gets smaller as this barrier gets bigger. Once you have built yourself an iron-56 nucleus this way, the barrier is just as big as the energy released, and the reaction will no longer proceed on its own.
