I think the thinking was that turning against Israel more publicly would have mostly garnered more entirely worthless votes in states that are already blue and risked losing at risk rust belt states

That’s just not true though. It would have helped across the board but especially in critical swing states

Here Are 34 Polls That Show A Ceasefire & Weapons Embargo Help Kamala Win

Kamala Would Have Won With A Weapons Embargo

The blame is entirely on the campaign for chosing to ignore and even go against those voters instead of make concessions to gain as much votes as possible. They chose to prioritize continuing the genocide over winning against Trump.