Communication is important for leaders, political and otherwise, for all sorts of reasons. If you’re a leader who is trying to lead major change, in an organisation or a political party or a country, communication is a particularly useful skill because it helps in managing that change, and because it helps to build the consensus which can support and sustain change. It’s also useful in terms of being able to hear all sides of the argument and take into account a wide variety of information, which tends to lead to better decision making. I don’t know whether Jeremy Corbyn consults widely and listens to other views than his own, but the evidence would tend to suggest he doesn’t.
Nor, at least based on the current state of the Labour Party, is he good at building consensus. Of course he has had to deal with a parliamentary party which has been against him.from the beginning, but he doesn’t seem to have done a great deal to engage with them and bring them on side. To be fair to Ed Milliband, who god knows was a pretty ropey leader, he too was a left wing leader elected against the wishes of the parliamentary party, and he managed to hold the party together for nearly five years.