I know my arch-right-wing childhood friend was raving about Corbyn back slightly before he even got his Momentum in gear. In hindsight, I can see he was attracted by the political disruption (similarly the whole "I agree with Nick", before that, despite definitely not being liberal, let alone Liberal - I don't think he was that much into Blair, though perhaps that's surprising for other reasons). It was the nascent radical populism that seemed most attractive.
While, for me, I distrust populism with a vengeance. I can be excited enough about opportunities to overturn the current messy status-quo situation that I disliked, which at one point Jeremy was (and Nick could have been, and Tony famously did) but I find it tends to revolve around single-issue focal points and even if I agree with that, it inevitably leaves a huge amount of unsatisfactory side-issues. Witness those wanting to get out of the EU with (as was proven) little idea of where to go from there (or even how to exit), if you'll forgive my raising that rusty old subject, and yet somehow barely scraping that result against what even I felt was an unattractive but competent opposing viewpoint (because it held no promise of any refreshing change).
And that was one of the things that wiped much of the Corbynite promise out vs. Johnson. Those who took the Euroskeptic view didn't get anything useful from him (though he tended towards that), because Boris just played that game better, as we saw. Those who were still sufficiently Europhile didn't get any chance of solace there either because he didn't want to or dare to actually give the reasons why not to just let the Tories go all bull-in-a-chinashop about it. And this translated into votes for/against local candidates that many have since regretted even if they "got what they wanted".
That and the rise in newsworthyness of his brother's antics (strangely he had no real press exposure when certain people were surely looking for dirt-by-association on Jeremy, or maybe there just weren't any big issues for him to come out of the woodwork for, at that time, by comparison with the more direct political monstering), and all that antisemitic mud-flinging/-sticking that went on, etc.
On the whole, I find much of this to be an inevitable but regrettable distraction. Because populism (or the corresponding counter-populism) is so baked in. It's how Salmond got his party where he did, and how Sturgeon has kept it there (after a short tricky stage where the differences between the two major sub-sects of supporters might have significantly rifted the support base in dealing with the situation that ultimately discredited the former), plus how the DUP seems to have kept itself relevent nationally despite effectively refusing to govern locally unless someone else picks up the toys it has been throwing out of the pram (which is an interesting contrast to Sinn Fein's longstanding stance).
And it's why right now I'd be quite comfortable with Starmer in power (not even counting how my Dad had been a friend/'colleague' of his Dad as part of the deal), because he exudes a true wide-ranging competance that few others show. Not Truss, not Johnson, not Corbyn, certainly... Begrudgingly I'd say Cameron actually did, and May probably, with Brown being more competent than Blair, but single-issue events/opponents levered them out of position. Cable worked for me (but on a hiding to nothing in the climate of politics he was the leader in), better than Clegg turned out to be or... whoever succeeded him (can remember he was religious, etc, can't recall his name - which probably says something - and they moved on again later, right?), and Welsh politics has had its "interesting" moments and figures but I'd have to check my recollections before pontificating on their situation alongside the other national/nation perspectives that I follow more closely (willingly or otherwise).
And it's why Tories should not want to force an early General Election, either directly or by having Truss backstabbed enough to make it her (or her successor's) spiteful choice to do so. They need to both try to recover (demonstrate how they are not a total car-crash) and let Labour build up the Starmaresque (or successor?) version of counter-populism to make it the same old battle between the worst (or definitely most polarising) bits of ideology that seems to be considered necessary in this day and age. And, I'll admit, certainly helps the eventual victors (or at least the king-makers who prop up the victors).
And 'Jezza' is not a current threat to the Conservatives, could never be, and surely cannot have helped his cause if (all else being equal) he had remained as leader after his GE collapse. I could see him fully supporting the inumerable strikes/work-to-rules, perhaps even orchestrating a new General Strike in all but name, but not sure that would be advantageous. Starmer maybe can be considered as over-cautious in this very same issue, but for good reasons. Vocally supporting the workers (and others) without going front-line on the picket-line is the best of various increasingly bad choices (IMO!), one or other of which Corbyn would likely have decided to take instead.
But there's much what-if, here. We can't see, for example, how Ukraine or the Pandemic or the Sub-Prime fallout or the post-911 or the Falklands War might have unrolled with alternate leaders, or if combined with a different timing of other events (parlimentary recesses, monarchical deaths, weather events, otherwise unconnected world-market tremors, etc) that may either add to pressures or temporarily distract from the other crises and their increasingly bumpy roads. It's much more down to who was at the reins of power, than who might even be leading the opposition, and I don't have my trans-dimensional televiewer plugged in right now (the fuse it needs is a bugger to obtain in this reality!) in order to compare with the world that resulrs from any given alternate history. But I definitely have some ideas about what isn't a better storyline than even the currently troublesome one.