it's a catch 22 situation where you can't have two minority picks because ostensibly, that would be DEI, but specifically picking a white guy for DEI is ostensibly not DEI because you're picking the best candidate for the role.
i don't really think it's any deeper than the fact that tim walz was literally the perfect pick, he just happens to be white. I'm not sure you would be able to find an equally beloved and respected pick other than him.
like, just so we're on the same page here, it's not a bad thing that she picked a white guy, it quite literally broadens and diversifies her running, i believe she also wants to appoint more diverse office candidates as well, so we'll probably see less white people there inevitably.
at the end of the day, it is what it is. You push for diversity in picking someone like Kamala, you also have to do the same thing for white people as well. It's all strategic at the end of the day, they wouldn't have done it if it didn't make any sense.