Starmer may have won the battle against Burnham for now but he is by no means guaranteed to win the war. The decision seems to have angered a lot of people in the party.
I think it was unwise for Starmer to cast a vote against Burnham. In the unusual circumstances, he would have been better off standing aside and leaving it to the rest of the NEC.
Another potential problem he has now is: what if Labour loses the by-election to Galloway or (worse still for Starmer) Reform? Presumably the candidate will now be a local activist hardly anyone has heard of before. If that candidate is defeated, the question will inevitably be asked about would the result have been different if Burnham has stood? He does have name recognition and seems to have a following in Manchester.
I can understand Starmer acting to clip the wings of a rival – but it is a risk with a potentially big down side.