Why does it take so much heat and pressure to create helium and other elements?

To break down the nucleus of an atom

Explanation:

Remember to change from one element to another, is necessary to add protons, neutrons and electrons,in most of the cases.

The take an electron from an atom you need certain energy, but they are in the outside part of the atom so is not as much energy as the one is necessary to take one neutron or proton from the inside part of an atom.

In this way, is a must to have a combination of pressure and heat to destabilize an atom and take some of this subatomic particles.

b i think it’s a water wheel turning in a stream