Loads of countries require mask wearing at a young age. My niece lives in spain and has sent photos of her 2 year old wearing masks without any issues. If something is required, you obviously need to spend time normalising it for your child if there could potentially be an issue. These parents didn't and, I suspect, decided to make a deliberate point of it.
Sure, some 2 year olds will object, the same way some will object to being put in a car seat or having the seat belt put on in the plane. As a parent, you then need to decide what is the best approach. Should you choose another method of transport? Should you practise with them in advance to normalise it? You don't just decide Feck it, I don't like the rule so I'll ignore it.
One of mine absolutely hated being in a car seat, even at that age. That was not an option so, despite many tears, we persisted. I expect most parents are the same and if they're not, they should be.