He was sadly too divisive to be a widely-popular Labour leader

Bullshit. He was elected leader because people wanted to go back to the party’s left wing roots.

The Blairite Neoliberal wing of the party didn’t like that, so they ousted him with a smear campaign calling him “divisive” (read: agrees more with the broader population than with the neoliberal establishment and their rich owner donors) and “antisemitic” (read: isn’t in the pocket of the fascist apartheid regime, has empathy for their Palestinian victims)