I think basically that Andy Burnham is perceived to have concentrated on domestic policy, and also really focused on Manchester needs. Whereas we have a country sliding into wwIII, really complex international situations to deal with, outcomes of which will have huge, huge impact on all of the UK including Manchester, and a large number of serious domestic issues, more pressing than devolution right now (as pointed out upthread) plus no infrastructure in place to deal with devolution and no money to pay for it.
If anyone actually wanted the UK to slide in wwIII right now for whatever reason, they will be delighted to have a PM who is focusing on devolution rather than saying no to unwise military decisions!
Ihave looked at Burnham's record on foreign policy and it seems he made a point of following the whip on everything, but keeping it to simple blank statements, which I think is something he will need to look again at. Good foreign policy decisions and leadership right now is so important, to keep us out of war and to increase sophistication when it comes to understanding all the different interest groups in relation to foreign affairs and in relation to negotiation, for the long term benefits of civilians everywhere.
As well as all of the many really difficult domestic issues to deal with - and again the various interest groups pulling/funding in different directions in relation to domestic issues.
We need a really well informed and capable PM right now, someone who understands all the strands, capable of critical thinking, wisdom, morality, someone with background knowledge, ahead of the game, IMHO.
The decisions taken in the next few months even will very much impact on every normal family in the north and the south and every part of the UK.