"Fabricator and a fraud" is an extraordinary claim, and requires extraordinary evidence.
The paragraphs handwaving the EHRC report in to antisemitism - which did absolutely find the party as an organisation to have failed to tackle antisemitism under Corbyn's leadership, as well as former leaders Miliband, Brown, Blair, etc - and trying to argue that Starmer describing as such was fabricated and/or fraudulent is false.
This is the problem with these sorts of things. Oborne isn't wrong when he says that Starmer failed to meet the expectations that he himself set, but fraud requires purpose and intent, neither of which are clear.
And let's be honest, the idea that Starmer and his team ran a competent conspiracy, whilst clearly demonstrating incompetence basically everywhere else, is a tad silly.