Anyone else leaving up a huge statue in the middle of the park would be arrested

It's not in a park. It's on the pavement area of a road. For better or worse they don't arrest many people for leaving stuff in the street in London. A fine maybe.

Presumably Banksy and associates would have been arrested too if they had been caught. This whole thing relies on doing it in a way that people don't question it while it's happening.

Yeah, and that is precisely the point.

This contradiction at the heart of it does a lot of work and is a very valuable part of the art. This contradiction has led me to think a lot about rules and their role in society and to what extent pure strict rules based societies are a worthwhile goal and on the other hand what it means of we make exceptions.

This is a joke right? If elon musk had done the same thing (which he obviously could) i don't understand what is the value