The intellectual case was less unified than the label suggested. Dennett wrote about religion as a natural phenomenon to be explained by ordinary means; Dawkins argued that the existence of a god is a scientific hypothesis and a poor one; Harris argued that moral questions have factual answers; Hitchens made a historical and moral case and was, principally, a polemicist of extraordinary skill. They agreed on the conclusion and differed on nearly everything else.
The criticisms were correspondingly varied: that the theology being refuted was a version no serious theologian held; that treating religion as primarily a set of propositions missed most of what religion does; and that the argument shaded repeatedly into hostility towards Muslims specifically.
The fracture, when it came, was not about God. In 2011 the blogger Rebecca Watson described being propositioned in a hotel lift at a conference in Dublin, and asked men in the movement not to do that. The scale of the backlash, and a sarcastic public dismissal by Dawkins, exposed a fault line that had nothing to do with theism. Atheism Plus, in 2012, proposed that atheism be explicitly coupled with feminism and anti-racism, and provoked immediate hostility from those who held that atheism meant nothing beyond disbelief.
Atheism Plus itself faded quickly. The split it named did not, and it is the reason the movement is now discussed in the past tense.
Hitchens took no public position in that argument, and died in December of the year it began.