This, in part, is a legitimacy crisis. If Labour won't follow the law and its own regulations when it doesn't suit them, then what's the purpose of the party that loudly promoted those those laws an regulatory body? Parties have to stand for something, you can only accomplish so much with messaging if you don't.
But it's also a political crisis of epic proportion. New Labour practically invented the modern age of political polling - tactical repositioning and re-framing to capture public sentiment. To poll at 14% isn't just undesirable, it's bewildering -it's like an animal that tracks by scent being caught in a forest fire. Where's the bottom? What does the Labour rump look like? Can Labour resist calls for a general election, especially if Starmer goes? Would ANY Labour MPs actually survive a general election? It makes just as much sense to say: "well, if we can win back half of the polling we lost to the Greens that would at least give us a floor", as it does to try and carve out Labour's center left, major party ruling stance.
Put differently, I'm sympathetic to Labour's plight, many of those in leadership are men and women of ability and principle and their decisions aren't easy, but in times of governing stress, sometimes you have to standard on principle and character - polling be damned. It's the right thing to do. And, usually, with some degree of irony, that stance is also the best thing (or least bad thing) to do from a polling perspective.