It is good news. I am glad the crew were rescued alive.
One of the other positive aspects of the story is an indication of more openness in dealings between Russia and the United States along with Britain. Long term, that will lead to better cooperation, and also a freer society in Russia.
As to why the Russian submarine was close enough to the cable to get tangled, it is most likely they were eavesdropping on the cable communications. We eavesdrop, they also eavesdrop, to verify official information coming from the other country. This verification does help to avert disastrous misunderstandings between the two countries.
Shades of Watergate? Just wait, they'll blame Nixon.