Scale is the really important thing here. It's really easy and really cheap to build a small-business, or home scale generation system.
This is in contrast to nuclear, coal, gas turbine etc where you really need large plants to work efficiently. Small portable diesel generators exist, but they are expensive to run, need regular maintenance and refueling.
Once you can cost effectively generate real electricity for very little effort, and very low cost, then people do it. And when you distribute generation like this very large effects happen very qickly.
This is in contrast to nuclear, coal, gas turbine etc where you really need large plants to work efficiently. Small portable diesel generators exist, but they are expensive to run, need regular maintenance and refueling.
Once you can cost effectively generate real electricity for very little effort, and very low cost, then people do it. And when you distribute generation like this very large effects happen very qickly.