Some loyalists are likely to have said they would resign shadow cabinet posts to give Corbyn cover to ignore members. And if he changed his mind so would they.
One, Corbyn chose to make no attempt to coalesce support around any serious alternative to Theresa May's Brexit.
Two, he chose not to gather support for PV.
And, three, it is those choices which leave Theresa May's Brexit as the only game in town.