Nunu is really, really strong in low elo.

I don't think they even think about objectives to begin with

I mean it's a part of his class's strengths. Wardens don't have any hard engage and outside of Galio lack any real chain cc. They're a lot like Juggernauts in that have make up for it by having much stronger tools.

That's what Nunu does. Take objectives.

He pays a huge price for that power; it's literally all he can do.

Everything is really, really strong in low ELO in the hands of a player that knows how to exploit bad players, zero strategy, trash map awareness and slow reaction times.