Trudeau won - as has already been said by you and others - because he was fitter and had a greater variety of punches. I didn't notice the grandstanding, which is something I dislike too.
As it happens, there was some "celebrity boxing"(between famous non-boxers) on German TV last night. They boxed under pro rules without head protection. I saw a couple and their boxing skills were no worse than those in the above bout. Trudeau at least moved well enough to stay out of trouble after the first round. Thinking about it, you are right about his jab. Had it been working properly, he need never have got into trouble at the beginning of the fight. I quite liked the reaction of Brazeau when he was asked what hurt worst!