All the answers are already in the article: gambling is illegal in Indonesia. It is a Muslim country, so the government will monitor anything and everything that is Haram and it's not the only Muslim that does that, so the action is pretty obvious on their part.
According to the article, Google's search engine is still working, maybe because they already censored it for Indonesians so they could retain their presence.
I think Duck Duck should follow Google's lead to enter Indonesia, which is to restrict or censor their search engine.