Corbyn wasn't just deeply unpopular across the country outside of student areas. I spoke to life long remainer lib dems in the Tory/Lab marginal seat of Crewe and Nantwich who were voting Tory to stop Corbyn. Across rural areas in Cheshire people were voting Tory because they were scared of Lib Dems backing Corbyn.
Due to the way that FPTP works, his concentrated support in student/young urban areas was wasted, with the result being a Tory landslide.
This describes me. Luckily I was able to meaningfully vote LibDem, because I really could not see myself voting for BoJo or Corbyn in the last election. Neither Starmer nor Sunak would be my first choice, but in contrast I could hold my nose and vote for either of them if I had to.
I spoke to many who similarly voted to stop Corbyn - they were stopping Corbyn because of his vow to reintroduce gas chambers and exterminate every Jew in the land. I am not sure that was his actual policy but many were adamant it was.
The naive elector sees Corbyn pissing off the Jewish groups on front pages everywhere, and or course they do not want to associate with people of that ilk. The majority trust newspapers and politicians too much, so get routinely played like a fiddle, and the best liar always wins.
The similar shit show is going to play out next election with Reform UK if the liar extraordinaire Nigel Farage decides to front it.
Setting aside that in 2019 under 15% of the country read a newspaper, it's a moot point. Part of the job of being leader of a political party, just like any business, is to handle public relations. Corbyn's team was awful at this. It's no good whining about it, you have to handle it.
Personally his pro-wealthy attacks on making the care system fairer were one major thing that turned me off. He spent a lot of political capital trying to defend the right of millionaires to not pay for their own care (and thus increasing everyone else's tax burden).
Millionaires paying for their own care is how you end up with a terrible, underfunded, and eventually privatised public care system.
Despite it being a policy supported by all sorts of economic think tanks from the IFS to Adam Smith, and has support from the Green party to the LSE, somehow he managed to completely bungle it and push the cause back a generation. Another thing I can't forgive him for.
I recall at some point last election cycle an interview with a very passionate gentleman in the north who was adamant that we had to "Vote for Change, its time to get Corbyn and his failed policies out of Downing Street". He was utterly certain that Corbyn had been prime minister for the prior four years and the terrible state of the country was down to him.
I am no fan of labour but that environment is not good for anyone and has ultimately (ironically) destroyed the Conservative party.