The advert was paid for. It was not news or editorial. It did not say Corbyn was antisemitic. Just that he was failing in his leadership, which is entirely a matter of opinion. The fact that it was written and paid for by a group of parliamentary peers who could afford a full page advert in a national paper speaks volumes about their motives. Just consider who will benefit and who will lose most in a Corbyn led Labour administration. I am pretty sure that rich career politicians are worried. Hence the barely concealed hatchet job.