1.
Personally, I think that the whole article was surprising in a way, and it is not easy to highlight something. But I was surprised, for example, that gorillas can lie, and the fact that it is natural for them is also surprising. But well, maybe I underestimated them.
2.
Generally, about everything.
3.
Because they want to look better in the eyes of others. It is also a defence against one's own vulnerability or it can basically just be a fear of reality.
4.
What matters to me is the intent or motivation of the lie. If you lie because you want to avoid emotional harm, it is excusable. If you lie, just for your own personal gain or with bad intentions, it's just wrong.