I don't think that's it. I think they saw democrats didn't like it when Biden gave money to Israel and so they switched to give their voters a feeling of hope that they might get a candidate that actually aligns with their values.
I've also noticed a huge uptick in social media "vote blue no matter who" rhetoric. This has been coupled with AI comment bots arguing against third party voting.
SO yes, I'm seeing a ton of shady corruption that I agree skews the voting, but I think you're missing just how it's done.
Which, because I'm voting third party, I'll suggest that you (nicely if you can) try to convince democrats to vote third party. It would benefit us both, as I'm not in favor of Kamala and neither are you. I don't foresee her winning anyway because of the polls either. Too many leftists don't want to vote for a cop. They don't trust her to actually block the government from taking more power or giving money for foreign powers.