I would have thought that you wouldn't even do root canal on a three year old; if the tooth was that bad they would just pull it out, and leave it until the second teeth came through, but maybe they need to keep the gap filled.....
The guy was a sociopathic charlatan, so I'm sure he was just ignoring things like common sense and standard procedures.
I also wonder a bit about the parents. Why would you greenlight so much dental work so early? Were they giving the kid nothing but chocolate or something?