So obvious and yet you’ve been completely unable to provide any coherent evidence for it across multiple threads of being asked for this.
Here’s something obvious: Labour were unpopular under Brown, unpopular under Miliband and actually saw their vote rise in 2017 under Corbyn, who presented some policies that were — gasp — popular. Here’s something else obvious: Labour’s biggest problem right now is trying to hold together the Brexit-voting base in the north of the country with their remain-voting support in the south, which is an issue not remotely of Corbyn’s making. You’ve swallowed a narrative of it being all about leaders in the face of all historical evidence. And in repeatedly insisting on it, you’re making an absolute tit of yourself.