I think you put too much blame on yourself.
Electricity can be very tricky and coming with mechanical background I learned lot of it the hard way.
One time had motorhome with build-in generator that with good batteries would not turn over.
It had good power when checking, but when pressing "start" all died.
Good thing it had slide-in railing as after days of frustration, I found that one of cable connection, looking very clean and torqued properly would allow voltage to pass at low amps, but would fail at high amp.
Took DW pressing the button and me with voltmeter going from one connection to other.
Those thing can be real nightmares.