I would not be surprised if an impetus for the current turmoil within Labour Parliamentarians is their grief for the loss of murdered colleague Jo Cox. It can be all too easy to want to 'lash out' at such a loss.
Author and former diplomat Craig Murray says the timing of this revolt against Corbyn is due to Blairites hating the prospect that Corbyn would be the Labour Leader in Parliament at the time of the delivery of the Chilcot Report. It's Still the Iraq War, Stupid
I would also point out that the foundations for many of the really nasty 'welfare reforms' that the Conservatives are now pushing through were really piloted by Blairites. In April 2010, Sheffield Forum reported that a much harsher test for the 'Employment & Support Allowance' that replaced 'Incapacity Benefit' had been authorised by then Work & Pensions Secretary Yvette Cooper. Even Harsher New ESA Medical Approved. That test was not piloted until early the following year, and so it eventually seemed as if it was those nasty Tories that were delivering it, when in fact it was Blairite Yvette Cooper.
Dude Swheatie of Kwug