Because there is quite a large range of views in the Party some Labour supporters will never be happy about the leader.I'm not sure Johnson's bluster and incompetence makes much difference to his voters ? It's not like they didn't know what they were getting,whereas Starmer...some Labour voters maybe hoping for better maybe.
We are stuck with the majority choice, and if or when they prove to be a dud they will be dropped. That’s democracy. It’s happened before, remember. It could well happen with Starmer, we shall see.