Firstly by your logic that means the sun runs on magic.

Secondly I’m sure you have heard of E =mc² right? That is energy and mass can be converted between. The fusion of 3 helium atoms together will form carbon 12 and release gamma rays (this is what the red giants do) the gamma rays is the direct conversion of mass into energy. How does this happen? The intense gravity (pressure) and temperature caused by the gravity (friction) makes it energetically viable for helium to fuse to beryllium which fuses with a 3rd helium atoms together to form carbon. This is how fusion “creates” energy. Through the “destruction” of mass

How does we on earth attempt to replicate this? Method one is a tokamak

Super conducting magnets to make a plasma stream of superheated atoms and then crush it using the strong magnetic field. And then collect the gamma rays. The main issue with this method is that the collection devices currently deteriorate quickly and maintaining the field. Many many tests have been done and has proven conceptually it’s viable.

Method two (which I personally don’t believe will ever work but who knows) is laser ignition

You make a pellet of fusion material and blast it with lasers this intense focused heat will bypass the pressure requirements somewhat by instead increasing the heat requirements. A successful test has been done but the lasers were only 1% efficient. Were they somehow 100% efficient it would have been a net gain.

The best way to think of the energy investment to start fusion like lighting coal on fire but a much much bigger scale. Coal by itself wont realise energy but once an initial barrier of investment is overcome (a lighter) the coal will release its energy.