It looks like a broken, rotting molar. The style is called, appropriately “Brutalist”. It is indeed ugly.
I think such “art” exists so talentless people can claim to be “artists” and create “art,” and also so that people without artistic taste or sense can wax ecstatic over something they do not understand so they can appear to have artistic “taste” to other people who, also lacking any sense of artistic taste or sense, are doing exactly the same thing.
That is the answer!
I always wondered, why would anyone do it. You know, artists are not rich, at least not rich when they start. No one starts thinking, -- "Let me do ugly things so that in a decade or so of trying I get paid for dropping an ugly thing in the middle of an old city that already has a beautiful cathedral". Why wouldn't he learn a trade instead?
We elevated the prestige of an artist and at the same time told everyone that they get a trophy just for trying. Modern art resulted.