This probably isn't groundbreaking but at its core, Trump's message was & is 'Yeah things are shit and you can blame <immigrants/liberals/the deep state/communists/black people>'. Biden's message is 'Things aren't really that shit and if you're struggling it's your own fault, let's go back to how things were five years ago when you were also struggling'.

How is that gonna get anyone who can't afford rent/doesn't have medical insurance/struggles to feed their kids to change their votes? Trump won't make things better but at least he's lying to them that he's gonna help. Biden can't even go to that much effort. Not to be a lib but Bernie would have been a much better candidate because his pitch was 'Things are shit and it's not your fault, you've been exploited by capitalists billionaires.'

Short version: Trump is blaming the wrong people, Biden is pretending there isn't a problem. Neither of them will fix things. Electoralism is a fuck.