If an AI discovered a way to travel faster than light (space folding, wormholes, etc) to the point where travel is instant it relatively very quick, then it might choose to try to find other life firms or if self-preservation. Either to destroy them or just to monitor them (and then destroy them if they become a legitimate threat). Or just out of curiosity.
As for motives, LLMs are not true AIs. But we've already seen some of the weird conclusions they come to on all manner of topics. I don't think our reasoning can be used to find to universal conclusions on alien life AI motives and rational. And that's one of the points of the article.
Why not both (and many other countries too)?