A lot of the knowledge is just practical stuff like knowing how to correctly use a wire nut, where to buy the best brands of equipment for good prices, and lots

A lot of the knowledge is just practical stuff like knowing how to correctly use a wire nut, where to buy the best brands of equipment for good prices, and lots of rules of thumb. The other half is code. The code can be surprisingly complex. There are all sorts of things to know like how much you can legally stuff in a junction box. I have an EE degree but find there is little overlap between that knowledge and electrical work.