My understanding is that the earliest stars would have begun to form only a few hundred thousand years after the event and begun to explode not terribly long af

My understanding is that the earliest stars would have begun to form only a few hundred thousand years after the event and begun to explode not terribly long after that on account of their mass and rapid reaction rate, seeding the early universe with some amount of nucleosynthesis product almost from the outset. Of course, I think it was rather a while longer before it cooled down enough for things other than raging thermonuclear fireballs to find hospitable.