TBF Dave there’s no need to allege collusion between anyone other than some of the PLP and the media.
The Tories will pile into any Labour splits anyway and the BoD were reacting to stories that were mostly planted by the anti-Corbyn group in the PLP.
If there had been a wider anti-Corbyn front of the kind you describe, AS would have been front and centre early on rather than being the one successful stick out of an awful lot that they tried to use against him. Don’t forget the ones they tried - him being to blame for Brexit, him being to blame for the culture of harassment at Westminster, him having links to pro-nonce groups and so on.