The Kamala campaign had one and only one major problem.
COVID stimulus and an economic slowdown from 2020 caused four years of inflation in the entire world, and people see the price of milk going up and punish the incumbent (not even the person who was in charge in 2020.
At which point, it doesn't matter how you campaign, or if the opposing candidate is actual Satan, nobody's going to vote for the incumbent.
It also doesn't help that the press normalized actual insanity that would not have been tolerated from anyone else, and collectively pretended that it's normal and reasonable behavior.
It does matter how you campaign. Very few people live without access to information beyond the price of milk. If you see that global inflation is a thing and that it is a topic of importance for potential voters you could acknowledge that it exists and work on your messaging/make it look like you're trying to do something to fix it.
The messaging that really gets through to people who can't understand that is naked, blatant lies. It worked with Brexit, and it worked yesterday.