His positions are in alignment with the majority of USians.

It doesn't matter. Politics isn't just about positions. It's also about alliances - who has your support, who you prioritize. Politics is about who you can rely on. Including, and arguably most importantly, in the disputes and debates about whose interests will be advanced within the coalition. El-Sayed might be right on the issues, but he won the primary without forming a strong alliance with the black community - for reasons below.

Once someone's elected, they're nominally free to make whatever choices they want. Communities are very concerned about making sure that they support politicians they can rely on to support their community - not the positions, but the choices they'll make on things that have far more impact than how they'll vote on a theoretical Medicare for All bill that will never pass or the Iran war that they have not control over. Namely, choices about which communities have more relative support in their office.

El-Sayed's choice to be part of Uncommitted was thus very consequential. That choice helped him build credibility and support in the Muslim community. That was very beneficial to him, especially in the primary. But that choice also eroded his credibility and support in the Black community. That was detrimental to him, especially in the primary.

The Michigan primary was in February. Biden was still running. The "uncommitted" vote was a protest against Biden's unquestioning support for what Israel was doing in Gaza. The primary was not about Harris.

Uncommitted deliberately withheld their endorsement from Harris. They didn't endorse Trump, but they very pointedly refused to endorse her. Which is certainly their prerogative. They felt it was far more important to send that message than to full-throatedly support her campaign. But one of the consequences of that is that the black community has a little less trust in that particular political faction of the larger party. That community heard the message that taking that stance over Gaza (which was unlikely to have any practical consequence) was more important than taking a stance to support Harris (which might not have had much practical consequence, but more than the Gaza position).

Sometimes in politics you have to make choices between groups that are both in your coalition, and often those are the most consequential choices and the most consequential signal of your priorities as politician. It's easy and obvious to take positions in favor of popular things, and that doesn't tell people much about how you'll make the choices that matter just as much (if not more) that are not easy and obvious.

Living in the Detroit 'burbs, I see how deeply bigoted a lot of people around here are.

No doubt. It has been ever thus. My very first political job was being on an advance team for the Dukakis campaign - ironically, in Detroit of all places. Not the 'burbs - Detroit itself. A few of my assignments were in union shops around there, and boy - yeah, it was deeply bigoted.

So I don't see why that would lead to any change in circumstances for the Democratic coalition. These "blue dot" communities aren't suddenly going to turn white nationalist. They're mostly minority districts. They're not going to become white nationalist communities.