As a head of state, he has a protocol office that is supposed to be on the alert for this sort of thing, precisely to avoid the sort of scandal that resulted.
As I said, I don't blame him personally because he obviously had no idea what was coming. Boo to his staff, they fell down on the job.
And boo also to the priest, who was on autopilot and not paying attention. He seems to be quite elderly, and he may have been completely discombobulated because it was a state funeral and a lot going on. An altar boy or deacon in attendance with a paten might have helped, but at a funeral where you know many non-Catholics are going to be in attendance it's the priest's responsibility to make a little announcement either before the Mass begins or after the Liturgy of the Word for the benefit of the non-Catholics present.
So I think we're pretty much in agreement. And, sadly, it is a scandal that so many young Catholics are poorly catechized or not instructed at all. That seems particularly prevalent in parishes that went all gooshy after VCII, trying to softpedal or ignore anything that made Catholics 'different'. Fortunately, when we converted we found a truly orthodox parish that has a very active instruction program for children AND adults.
My daughter was in the first class of confirmands that were presented to our new archbishop after his installation. As a new broom, I guess, he decided that he was going to catechize the kids, live and on open mike in the service!!!! -- to say that our Parochial Vicar and Christian Education supervisor were collectively having kittens is an understatement! Fortunately the kids had been well instructed and absolutely nobody muffed their questions (big sighs of relief from the PV and our Sunday School lady).
You are almost correct about the protocol. The Prime Minister is Head of Government, not Head of State. In Canada, Her Majesty the Queen of Canada, is the Head of State. Her Excellency the Governor General of Canada acts on Her Majesty’s behalf when the Queen is out of the country.
Unlike here in the US where The President serves as both Head of State (symbolic leader of the nation) and Head of Government (the person who administers the government and sets policy), in Canada and most other nations, those two offices are separate.