Yes racism plays a part but it doesn't explain why Obama has outperformed Harris and why voters were unaware of the facts on key issues
They are bombarded with right wing content and disinformation everywhere they look online
Obama is a male half black and half white Harvard grad who is able to code switch with the best of them and started off on the grassroots level and built his way up to Senator and the presidency off the incredible charisma and brilliant campaign strategy he had. This made him appealing to both black and white people.
Kamala is a female half black and half Indian and big ups that she went to an HBCU. None of that appeals to white people. She adopted a white family by marrying into it hoping it would strengthen her ties to the white community. She is not a charismatic speaker, her strengths lie elsewhere. She also got destroyed withdrew from the primaries when she was trying to run her own campaign for the democratic nomination in 2020.
While the social media content does play a part Obama and Kamala are basically apples to oranges candidate wise. Obama was wanted the whole way through the process to being on face of the democratic ticket.
Kamala was basically told to kick rocks by poll numbers in 2020 and lucked into a VP pick. During her tenure as VP she didn't stand out much unfortunately and putting her as the face of the ticket due to Biden stepping down was not a great move.
Her support never felt organic or had any genuine enthusiasm we were mostly really like "fukk Trump let me vote for her". It's kinda like in sports where they tell you to "play to win" and don't "play not to lose". It feels like Dems are always "playing not to lose" lately. If I'm being honest.
I was hoping people hated Trump enough to just try and keep him out of office but I guess this isn't 2020 anymore that ship sailed. I think she would've been a decent president tho. Her other strengths are underrated.