I think he has changed - with Brexit and the lack of a strong leader he thought his offer of help and support to his old party would be welcomed with open arms, only to find he was not wanted - the penny has sunk in that everyone dislikes him for the way he set out to promote himself and make a fortune from day one of being PM and beyond, even if he was just using the system and doing nothing illegal. Perhaps there was some jealousy at his success as well. Now he seems to be humbled and chastened, possibly even hurt by being dismissed out of hand, when ironically his experience with the various Foundations he runs, and international contacts, etc, probably put him in the perfect position to help, or even lead, in the present crisis - certainly to do better than the current gang divided as they are, amongst themselves.
I say this as someone who has never voted Labour!