I think when one ahs read the parliamentary report into bullying in the labour party and the treatment of Diane Abbott , one realises that Keir Starmer is just as capable of 'tactics' and positioning and conniving as the rest of them.
I think seeing Burnham as a backstabber and Keir as some kind of wounded pure soul is probably naive.
I'm the rare find on MN of a Corbynite - Starmer did an awful lot of politicking to remove him (many people say rightly so : notwithstanding , tactics were deployed). Perhaps no one cares much about that because 'But Corbyn'.