Anyone can make a mistake, but thats' a pretty bad one.
Unless he was trying to replicate a jacuzzi.
Joking aside, it's only easy if you knwo the answer as Tarrant said. Plenty of people don't know a lot about electrics. I heard a lad once ask what happens when the power runs out on a pushbike dynamo.
I saw a youtube video of a fella who investigates badly made leccy appliances. One of them was a mains usb charger, but it had a short in the transformer and the metal outer part of the actual usb socket had 240 volts on it.
Check out this channel:
https://www.youtube.com/channel/UCtM5z2gkrGRuWd0JQMx76qA
He loves pulling apart cheap Chinese electronics, chargers are good ones.
Yeah, that's the chappy.
Anyway, if you really want danger, you wanna try repairing your heated drivers seat using some old jump leads and a big roll of wire wool. Make sure you bypass the fuse or it won't work. And ideally, you need to live quite near a fire station.