Even at large corps, it's fairly common to outsource IP work to law firms that specialize in IP - and if you're Danish, it might make sense to outsource to a Danish law firm that has its own worldwide IP contacts (rather than getting your own worldwide branch offices to handle local IP laws everywhere). One of said contacts might then pawn off the work onto a junior, who then has their assistant handle all communiques from CIPO. Said assistant could then entirely drop the ball.
I've zero idea about anything specific to Novo Nordisk, but have enough exposure to IP in Canada to envision the above happening in other cases.
That may be true if IP is not your core business but it is basically the core business of pharmaceutical companies. I don't speak from experience but it would seem surprising to me that any major pharma would outsource IP protection in a major market to contractors they can't sue for billions if they mess up.
It seems much more likely to me that they did it on purpose, as they claim to have.