Burnwinter Starmer's approach can probably be credited with sweeping a diverse range of seats despite a lukewarm vote.
But that's how elections are won - whether you think the system is fair or not. Theresa May had more of the popular vote than David Cameron ever did and was just shy of Boris Johnson's popular vote but she's remembered as someone who was a political disaster because it never translated into seats.
It's true that the manifesto Labour ran on in 2019 was benign but both Corbyn and McDonnell spent the past 30 years making their views known, their voting records are public and no one really felt that they would reel it in once they got into power and actually the 2017 election success prevented that introspection. Obviously I would have preferred Corbyn over Johnson but, genuinely, he got out maneuvered badly in 2019 by the Tories as a whole lot of people mistakenly thought Boris was unelectable even though he's never lost a vote.
goon Patrick Vallance as Science Minister too. It's refreshing to see these roles given to people with some understanding of the field and not as a political reward, or worse, on the basis of whether they voted Remain/Leave