Because you now did it to yourself.
They’ve used the same strategy for literally decades and it has only ever worked once. That strategy is “our candidate is not the bad one”. And it worked in 2020 simply because that year was absolutely fucked and lots of people were looking for someone to “fix it”. Joe Biden might as well have been anyone in that moment. In previous years it…has…always…failed. It failed spectacularly with Mondale, it failed with Al Gore, it failed with John Kerry (honestly, you could had stood up a loaf of bread with arms and legs with a big D spray painted on it and it would have had a better chance than that milquetoast dipshit). It failed with Hillary, and it has now once again failed with Harris. People don’t come out to vote against a candidate. And never have. The base shows up sure, but they always will. But the unlikely voters or centrists only show up to vote for someone they believe in.