I know quite a lot of lefties who joined the party in the Corbyn era, who became active in their local CLPs, who did a lot of canvassing and campaigning. And since Corbyn was ousted, most of them have not only disengaged from being actively involved in their CLP, but have left the party. Some relatively recently.
Some of those 'Corbynistas' still clung on, hoping to help maintain a foothold for the left in a party increasingly veering rightwards, towards and even beyond the centre. I think for them, their political engagement wasn't about personality politics, they didn't so much get on board with the cult of Corbyn as it's (mis)represented, although arguably many younger folk did.
Most of the ones I knew who hopped on the Corbyn bandwagon were in their thirties and above, already politically engaged, albeit through campaigning over any number of single issue campaigns: housing, anti-arms trade/militarism, environment and climate change, workers rights and trade unionism, etc.
It wasn't so much that they believed in Corbyn like the cultish figure he's made out to be, like some political Piper of Hamlyn, leading the party and everyone in it to a far-left political wilderness. He wasn't leading them left, they were already in and of the left. It was more that he mirrored and capitalised on their existing beliefs and activities. He represented lefties like them. And it had been a long time since they'd felt they had that kind of representation in parliament and the constituency Labour Parties, and in terms of the public and wider society.
Corbyn was both popular and populist (the latter in the original/broader sense, rather than the right-wing rabble-rouser sense).
But now many of those Corbynistas, who didn't so much believe in Corbyn like the quasi-religious figurehead of a movement, but more saw him as representative of their existing beliefs and political identity and principles, have drifted away.
It seems the party thought expelling - or the political equivalent of constructive dismissal, forcing out - lots of Corbynistas meant they would regain control of their party and lots of centrists who'd been turned off by Corbyn and the left would come flocking back to the party. But that hasn't happened.
In any event, Labour has always taken working class people and people on the left for granted. And that didn't matter so much. But the working class and those on the broader left still mostly saw the Labour Party as their party when it came to voting in elections. It was a bit like football colours, they were red, just because they were red.
But now many of those from the Corbyn era are now declaring themselves politically homeless, and saying they can't vote for Labour because it doesn't represent them, and because the way Corbyn was treated was shameful - but that's tokenism, in the sense that being critical of how the parliamentary party and the executive treated Corbyn is, by extension, a criticism of how they, the people who joined and got actively involved and expended so much time and energy in attending meetings and canvassing and campaigning etc were also treated so shamefully.
It's hard to come back from that. It's one thing for Labour to take for granted the votes of the working class and those more vaguely on the left without party political affiliations, and it's another for Labour to take for granted the votes of those who in recent memory were stabbed in the back by the very same party that now wants to rely on/take for granted its votes. Many are declaring themselves politically homeless and while some might hold their nose and vote for Labour, there will be many who abstain or protest vote for smaller leftist parties or Green or whatever.
And I think Labour haven't woken up to that, I think they still think those people who they've been so vindictive towards and ousted or driven out of the party somehow still owe Labour their vote, because who else are they going to vote for, right? Erm, no one.
And as well as the lefties who were part of the Corbyn surge in party membership and political engagement and activity whose votes can no longer be taken for granted...
...there are also the gender critical feminists. I know a fair few. Again, talking about being politically homeless. And these are women who haven't been and aren't bigots. Some have been involved in radical feminist politics for years. They're raging lefties to their core. Yet they now feel that Labour doesn't necessarily represent or safeguard the interests of women, ie women who were born women/assigned female at birth.
Again, there are many people whose votes Labour could previously have taken for granted, who are now saying that they don't feel any mainstream political party represents them or their concerns, and there's lots of talk of abstentions.
I suspect that Labour is underestimating and not properly taking account of how significant and issue this is to many women. I have friends around the country, who don't know each other but either speak out publicly or privately about the erosion of protections for women. It's not just the odd one or two people, there's a fair few, from different job sectors, different parts of the country, but all lefty types, more or less politically engaged, some having been activists and campaigners relating to different humanitarian issues, and some who are more vaguely lefty but not previously politically active but who are speaking out.
I think Labour might be in for a shock as to how so many of the voters whose votes they'd previously taken for granted will now be abstaining or spoiling their vote or voting for other candidates.
I think these two reasons are partly why Labour has been doing so badly in the polls, plus Starmer has all the charisma of a damp squib.